Go Back  Bike Forums > Bike Forums > Mountain Biking
Reload this Page >

Front Rear Tire differential

Notices
Mountain Biking Mountain biking is one of the fastest growing sports in the world. Check out this forum to discuss the latest tips, tricks, gear and equipment in the world of mountain biking.

Front Rear Tire differential

Old 04-12-19, 04:34 PM
  #1  
SoldSpartan
Senior Member
Thread Starter
 
Join Date: Jul 2018
Location: Hoschton GA
Posts: 94
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 41 Post(s)
Likes: 0
Liked 2 Times in 2 Posts
Front Rear Tire differential

So the front and rear tires on my mountain bike are made from two different manufactures and the front tire says to keep the tire pressure between 26psi-54psi. The rear tire says to keep it between 30psi and 45psi. So I figure to keep the front and rear tires at 30psi; is this the right idea?
SoldSpartan is offline  
Old 04-12-19, 04:42 PM
  #2  
79pmooney
Senior Member
 
79pmooney's Avatar
 
Join Date: Oct 2014
Location: Portland, OR
Posts: 12,830

Bikes: (2) ti TiCycles, 2007 w/ triple and 2011 fixed, 1979 Peter Mooney, ~1983 Trek 420 now fixed and ~1973 Raleigh Carlton Competition gravel grinder

Mentioned: 128 Post(s)
Tagged: 0 Thread(s)
Quoted: 4745 Post(s)
Liked 3,861 Times in 2,510 Posts
Keep the tires below that maximum and with enough air to keep from pinch flatting. The minimums on the tire are just suggestions. Are the tires the same size? Are they similar type? If not, play with the pressure until they feel right. In general, a little less air in front works out best since you put less weight on the front. I generally use 5-8 psi less in front if the tires are the same size and type.

Ben
79pmooney is online now  
Old 04-13-19, 09:59 PM
  #3  
enveous
Banned.
 
Join Date: Apr 2019
Posts: 58
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 45 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Not enough information.

Optimal tire pressure will depend on:

Tubed or tubeless
Tire size
Casing type
Rim width
Rider weight
Terrain
Aggressiveness of the rider
enveous is offline  
Old 04-15-19, 09:10 AM
  #4  
prj71
Senior Member
 
Join Date: Jun 2015
Location: North Central Wisconsin
Posts: 4,601
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 2965 Post(s)
Liked 1,167 Times in 763 Posts
30 psi is a little high for mountain bike use. ~25 is more reasonable for single track riding.
prj71 is offline  
Old 04-15-19, 09:20 AM
  #5  
enveous
Banned.
 
Join Date: Apr 2019
Posts: 58
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 45 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by prj71
30 psi is a little high for mountain bike use. ~25 is more reasonable for single track riding.
How much does the OP weigh?
What tires are they using (size, casing, tubes/tubeless)?
What rims?
Are they riding buff singletrack at mellow speeds or charging nonstop chunk?
Do they "ride light" or are they proverbial bull in a china shop?

Depending on the answers to those questions, ~25 psi may or may not be reasonable.
enveous is offline  
Old 04-15-19, 09:29 AM
  #6  
rumrunn6
Senior Member
 
rumrunn6's Avatar
 
Join Date: Jul 2008
Location: 25 miles northwest of Boston
Posts: 29,528

Bikes: Bottecchia Sprint, GT Timberline 29r, Marin Muirwoods 29er, Trek FX Alpha 7.0

Mentioned: 112 Post(s)
Tagged: 0 Thread(s)
Quoted: 5219 Post(s)
Liked 3,564 Times in 2,331 Posts
exact #s aside, maybe squeeze them with your eyes closed? the front should feel softer. I like to look at the rear tire as I roll, to see how much it is deforming under my weight. I don't want a pinch flat but I also want some strength & weight bearing. plus if the trail is a harder pack variety I can go a little faster if the rear is a little harder than what I would use on softer ground. it's been surprising for me to see how low I can ride w tubed 29x2.25 Riddlers. I think they're at 21 front 25 rear
rumrunn6 is offline  
Old 04-15-19, 01:19 PM
  #7  
hig4s
Senior Member
 
hig4s's Avatar
 
Join Date: Jul 2015
Location: Florida
Posts: 662

Bikes: Evil Insurgent, Giant Stance, Wife has Liv Cypress, son has Motobecane HT529

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 93 Post(s)
Liked 7 Times in 6 Posts
For best traction on technical and soft surfaces I usually keep lowering my tire pressure until they either start feeling squirmy on the corners, or start getting pinch flats on obstacles. I run Maxxis Ardents on one bike and Maxxis Minions on the other, both with tubes. For me this ends up being 20 to 22psi front and 25 to 28psi rear.
hig4s is offline  
Old 04-16-19, 08:42 AM
  #8  
prj71
Senior Member
 
Join Date: Jun 2015
Location: North Central Wisconsin
Posts: 4,601
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 2965 Post(s)
Liked 1,167 Times in 763 Posts
Originally Posted by enveous
How much does the OP weigh?
What tires are they using (size, casing, tubes/tubeless)?
What rims?
Are they riding buff singletrack at mellow speeds or charging nonstop chunk?
Do they "ride light" or are they proverbial bull in a china shop?

Depending on the answers to those questions, ~25 psi may or may not be reasonable.
There is no magic number, but ~25 psi works well in most cases for most people. 30 psi is too high.
prj71 is offline  
Old 04-16-19, 10:32 AM
  #9  
enveous
Banned.
 
Join Date: Apr 2019
Posts: 58
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 45 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by prj71
There is no magic number, but ~25 psi works well in most cases for most people. 30 psi is too high.
So when I ran 32f/35r psi in 2.3 Kujos, with DH casings, tubed, mounted on Mavic 317s they were too high? Why did I double pinch flat then? Why did I get tire flop at lower pressures?

Here's my buddy riding 30 psi on his Knolly, why is 30 psi too high for him? He's run lower but had issues with squirm and flatting.


Again, there are many variables that come in to play when getting to the right pressure. Variables that you either don't understand or choose to ignore.




enveous is offline  
Old 04-16-19, 11:55 AM
  #10  
prj71
Senior Member
 
Join Date: Jun 2015
Location: North Central Wisconsin
Posts: 4,601
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 2965 Post(s)
Liked 1,167 Times in 763 Posts
Do you know the difference between a general recommendation and hard and fast rules?
prj71 is offline  
Old 04-16-19, 12:16 PM
  #11  
enveous
Banned.
 
Join Date: Apr 2019
Posts: 58
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 45 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by prj71
Do you know the difference between a general recommendation and hard and fast rules?
Yes, and "30 psi is too high" is a specific recommendation,

Here are some general recommendations-

"Optimal tire pressure will depend on:

Tubed or tubeless
Tire size
Casing type
Rim width
Rider weight
Terrain
Aggressiveness of the rider"
enveous is offline  
Old 04-17-19, 08:39 AM
  #12  
prj71
Senior Member
 
Join Date: Jun 2015
Location: North Central Wisconsin
Posts: 4,601
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 2965 Post(s)
Liked 1,167 Times in 763 Posts
Ugh. You are obtuse. I'm not denying all of that comes into play. Those are hard and fast recommendations for the biker that is a tire geek.

For the general public that doesn't want to deal with figuring all of that out...25 psi is a good safe number for traction and rolling resistance. Assuming we aren't talking about a 300 lb rider.

And generally speaking 30 psi is too high. Especially on a hard tail as it would be like riding a bucking bronco.

Last edited by prj71; 04-17-19 at 08:50 AM.
prj71 is offline  
Old 04-17-19, 09:05 AM
  #13  
enveous
Banned.
 
Join Date: Apr 2019
Posts: 58
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 45 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by prj71
And generally speaking 30 psi is too high. Especially on a hard tail as it would be like riding a bucking bronco.
Nah. It depends.

For example:

The rigid bike in the video above is running 40f/45r which are good pressures for a 175 pound rider running 40mm tires on tubeless i25 rims on that trail. On the same trail (below, starting at 0:14), 18f/20r are good pressures ona FS bike when running 2.5 tires with reinforced casings on i35 rims.


"Optimal tire pressure will depend on:

Tubed or tubeless
Tire size
Casing type
Rim width
Rider weight
Terrain
Aggressiveness of the rider"

Last edited by enveous; 04-17-19 at 09:17 AM.
enveous is offline  
Old 04-17-19, 05:20 PM
  #14  
Bigbus
Very Senior Member
 
Join Date: Mar 2018
Location: Always on the Run
Posts: 1,211

Bikes: Giant Quasar & Fuji Roubaix

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 413 Post(s)
Liked 343 Times in 244 Posts
I've never had the same tire on the front and rear of any of my bikes at the same time. Is that even possible?
Seriously, I usually run a slightly wider and softer (less pressure) tire on the front and a more aggressive and heavier tire on the rear. Everyone has their own preferences and what works for them may not work for all.
Bigbus is offline  
Old 04-26-19, 03:14 AM
  #15  
Kapusta
Advanced Slacker
 
Kapusta's Avatar
 
Join Date: Feb 2017
Posts: 6,187

Bikes: Soma Fog Cutter, Surly Wednesday, Canfielld Tilt

Mentioned: 26 Post(s)
Tagged: 0 Thread(s)
Quoted: 2749 Post(s)
Liked 2,516 Times in 1,422 Posts
Originally Posted by prj71
Ugh. You are obtuse. I'm not denying all of that comes into play. Those are hard and fast recommendations for the biker that is a tire geek.

For the general public that doesn't want to deal with figuring all of that out...25 psi is a good safe number for traction and rolling resistance. Assuming we aren't talking about a 300 lb rider.

And generally speaking 30 psi is too high. Especially on a hard tail as it would be like riding a bucking bronco.
25 psi front and rear would leave me with near constant pinch flats in the rear with a tubed tire up to 2.4”. I weigh 175. I know this from experience.

There is no “generally speaking” with tire pressure without knowing at the minimum rider weight and tire size and to a lesser extent tubed or tubeless.

Bit if you are going to make an across the board rec without taking into account tire size, tubeless/tubed, and rider weight, 25 is too low. That is going to leave a lot of people with flats. Also rear should be higher than front.

Its like recomending size 10.5 shoes without knowing anythinng about the individual because that is the average men’s shoe size.
Kapusta is offline  
Old 04-26-19, 03:17 AM
  #16  
Kapusta
Advanced Slacker
 
Kapusta's Avatar
 
Join Date: Feb 2017
Posts: 6,187

Bikes: Soma Fog Cutter, Surly Wednesday, Canfielld Tilt

Mentioned: 26 Post(s)
Tagged: 0 Thread(s)
Quoted: 2749 Post(s)
Liked 2,516 Times in 1,422 Posts
Originally Posted by hig4s
For best traction on technical and soft surfaces I usually keep lowering my tire pressure until they either start feeling squirmy on the corners, or start getting pinch flats on obstacles
THIS^^^^ is the correct answer!
Kapusta is offline  
Old 04-29-19, 08:58 AM
  #17  
prj71
Senior Member
 
Join Date: Jun 2015
Location: North Central Wisconsin
Posts: 4,601
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 2965 Post(s)
Liked 1,167 Times in 763 Posts
Originally Posted by Kapusta
25 psi front and rear would leave me with near constant pinch flats in the rear with a tubed tire up to 2.4”. I weigh 175. I know this from experience.

There is no “generally speaking” with tire pressure without knowing at the minimum rider weight and tire size and to a lesser extent tubed or tubeless.

Bit if you are going to make an across the board rec without taking into account tire size, tubeless/tubed, and rider weight, 25 is too low. That is going to leave a lot of people with flats. Also rear should be higher than front.

Its like recomending size 10.5 shoes without knowing anythinng about the individual because that is the average men’s shoe size.
I just did a 13 mile ride yesterday on my hardtail with 29 x 2.4 tubed tires on old school single track...lots of rocks and roots. Rear was at 25 psi and front was at 23 psi. I weigh close to 190 lbs geared.

How in the hell are you pinch flatting unless you have thin sidewalls on your tires.
prj71 is offline  
Old 04-29-19, 09:54 AM
  #18  
Kapusta
Advanced Slacker
 
Kapusta's Avatar
 
Join Date: Feb 2017
Posts: 6,187

Bikes: Soma Fog Cutter, Surly Wednesday, Canfielld Tilt

Mentioned: 26 Post(s)
Tagged: 0 Thread(s)
Quoted: 2749 Post(s)
Liked 2,516 Times in 1,422 Posts
Originally Posted by prj71
I just did a 13 mile ride yesterday on my hardtail with 29 x 2.4 tubed tires on old school single track...lots of rocks and roots. Rear was at 25 psi and front was at 23 psi. I weigh close to 190 lbs geared.

How in the hell are you pinch flatting unless you have thin sidewalls on your tires.
Well first of all, looking at a single ride does not tell you much, but I will give you the benefit of the doubt that what you mean is that you do this all the time and never pinch flat.

In any event, there are a number of possible reasons:

Maybe I have more square edged hits. Maybe I ride faster. Maybe my sidewall or tubes are in fact thinner. Maybe you are a smoother rider.

I will say this though, I think my situation is more common than yours. Back in the day when we were all running tubes, I usually got away with lower pressure than most people.

Just because something works for you, does not make it the norm “generally speaking”. Telling the OP that his pressure is too high without knowing at the very minimum his weight and tire size is truly shooting in the dark..

Last edited by Kapusta; 04-29-19 at 11:31 AM.
Kapusta is offline  
Old 04-29-19, 11:07 AM
  #19  
79pmooney
Senior Member
 
79pmooney's Avatar
 
Join Date: Oct 2014
Location: Portland, OR
Posts: 12,830

Bikes: (2) ti TiCycles, 2007 w/ triple and 2011 fixed, 1979 Peter Mooney, ~1983 Trek 420 now fixed and ~1973 Raleigh Carlton Competition gravel grinder

Mentioned: 128 Post(s)
Tagged: 0 Thread(s)
Quoted: 4745 Post(s)
Liked 3,861 Times in 2,510 Posts
Originally Posted by Bigbus
I've never had the same tire on the front and rear of any of my bikes at the same time. Is that even possible?
Seriously, I usually run a slightly wider and softer (less pressure) tire on the front and a more aggressive and heavier tire on the rear. Everyone has their own preferences and what works for them may not work for all.
It is but you have to find one of those rare 700I tires. (The English version. 700 tenths of an inch or 70" diameter. They made those tires 140 years ago for high-wheelers. ) Twist it into a figure 8. Now you can have one loop going around the front wheel and the other around the rear. It's not ideal. Tends to rub on the BB. But you do have real all wheel drive. Problem is that the front rotates backwards. It's still a concept in progress.

And if you believe any of this, well I don't know what to say.

Ben

Last edited by 79pmooney; 04-29-19 at 11:13 AM.
79pmooney is online now  
Old 04-29-19, 04:28 PM
  #20  
Bigbus
Very Senior Member
 
Join Date: Mar 2018
Location: Always on the Run
Posts: 1,211

Bikes: Giant Quasar & Fuji Roubaix

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 413 Post(s)
Liked 343 Times in 244 Posts
Originally Posted by 79pmooney
It is but you have to find one of those rare 700I tires. (The English version. 700 tenths of an inch or 70" diameter. They made those tires 140 years ago for high-wheelers. ) Twist it into a figure 8. Now you can have one loop going around the front wheel and the other around the rear. It's not ideal. Tends to rub on the BB. But you do have real all wheel drive. Problem is that the front rotates backwards. It's still a concept in progress.

And if you believe any of this, well I don't know what to say.

Ben
If it's on the internet it must be true-those are the rules!!!!
Bigbus is offline  
Old 04-29-19, 07:31 PM
  #21  
hig4s
Senior Member
 
hig4s's Avatar
 
Join Date: Jul 2015
Location: Florida
Posts: 662

Bikes: Evil Insurgent, Giant Stance, Wife has Liv Cypress, son has Motobecane HT529

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 93 Post(s)
Liked 7 Times in 6 Posts
Really tired (yes it could be a pun) of hearing how 25 psi is too low.. I weigh 200 without gear, and always wear a backpack/hydration-pack, so I am at about 225 total. I have been running 25 front and 23 rear on both my trail bike with 27.5 x 2.25 tires and on my enduro bike with 27.5 x 2.4 tires now for four years. I have had 3 pinch flats, all on my trail bike, and all because I was trying to navigate 10 in high trail obstacle with a sharp edge and did it incorrectly.
hig4s is offline  
Old 04-29-19, 08:56 PM
  #22  
Kapusta
Advanced Slacker
 
Kapusta's Avatar
 
Join Date: Feb 2017
Posts: 6,187

Bikes: Soma Fog Cutter, Surly Wednesday, Canfielld Tilt

Mentioned: 26 Post(s)
Tagged: 0 Thread(s)
Quoted: 2749 Post(s)
Liked 2,516 Times in 1,422 Posts
Originally Posted by hig4s
Really tired (yes it could be a pun) of hearing how 25 psi is too low.. I weigh 200 without gear, and always wear a backpack/hydration-pack, so I am at about 225 total. I have been running 25 front and 23 rear on both my trail bike with 27.5 x 2.25 tires and on my enduro bike with 27.5 x 2.4 tires now for four years. I have had 3 pinch flats, all on my trail bike, and all because I was trying to navigate 10 in high trail obstacle with a sharp edge and did it incorrectly.
Nobody is saying 25 is too low. They are saying you can’t say that 25 (or any pressure) is the pressure that works for most people.

Why do you run more pressure in the front than the rear?
Kapusta is offline  
Old 04-30-19, 07:25 AM
  #23  
prj71
Senior Member
 
Join Date: Jun 2015
Location: North Central Wisconsin
Posts: 4,601
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 2965 Post(s)
Liked 1,167 Times in 763 Posts
Originally Posted by Kapusta
Well first of all, looking at a single ride does not tell you much, but I will give you the benefit of the doubt that what you mean is that you do this all the time and never pinch flat.
This is correct. My hardtail is the only bike I haven't converted to tubeless yet.

Maybe I have more square edged hits. Maybe I ride faster. Maybe my sidewall or tubes are in fact thinner. Maybe you are a smoother rider.
Could be. I don't know. Strava says my average speed was 7.1 mph. I'm using q-tubes super light and Schwalbe Racing Ralphs.

https://www.jensonusa.com/Q-Super-Light-29-Tube

Just because something works for you, does not make it the norm “generally speaking”. Telling the OP that his pressure is too high without knowing at the very minimum his weight and tire size is truly shooting in the dark..
What I've been trying to say along along is that 25 psi is good starting point that works for most of the general public all the time. But some people try to dissect it too much when all I was doing was making a generalization. Start there than go out and experiment and fine tune. Optimum for 29er tires is between 18 and 28. 30+ is way too much unless you are riding gravel trails or smooth machine built single track with little to no features.

In the end the reality of the situation is that whatever pressure is chosen you are choosing a trade off between rolling resistance and grip.
prj71 is offline  
Old 04-30-19, 10:37 AM
  #24  
Kapusta
Advanced Slacker
 
Kapusta's Avatar
 
Join Date: Feb 2017
Posts: 6,187

Bikes: Soma Fog Cutter, Surly Wednesday, Canfielld Tilt

Mentioned: 26 Post(s)
Tagged: 0 Thread(s)
Quoted: 2749 Post(s)
Liked 2,516 Times in 1,422 Posts
Originally Posted by prj71
What I've been trying to say along along is that 25 psi is good starting point that works for most of the general public all the time. But some people try to dissect it too much when all I was doing was making a generalization. Start there than go out and experiment and fine tune. Optimum for 29er tires is between 18 and 28. 30+ is way too much unless you are riding gravel trails or smooth machine built single track with little to no features.

In the end the reality of the situation is that whatever pressure is chosen you are choosing a trade off between rolling resistance and grip.
I understand what you are saying, and what I am saying is that it is not true. You are giving out bad advice, based on bad assumptions. Without knowing someones weight and tire size, you have NO IDEA what the optimum tire pressure is, and you had absolutely no basis to say that 30 was too high for the OP. You were shooting blindfolded in the dark. The range that "most people" run (which are numbers you are just making up based on almost no data), regardless of weight or tire size is utterly meaningless to any individual trying to get an of what pressure to run or even where to start. 30 PSI is ABSOLUTELY withing the range that some people end up. You just heard from a several in this thread. Were I running 2.1-2.2 tubed, I would be around 30, if not a little more.

And you are wrong about what the trade-off is. In mountain biking, it is not rolling resistance vs traction: The primary drivers are traction vs pinch flats and loss of stability, which means that you may need to run higher pressure in rougher terrain and for more aggressive riding. Look at what most DH or Enduro racers are running: 2.3-2.5 tubeless tires, with sturdy sidewall. Visit some forums and look at the pressures they are running: mid 20s to low 30s is typical. Some higher.

The proper advice was given elsewhere in this thread: start high, and slowly lower until you find where you are either getting pinch flats or tires squirming.
Kapusta is offline  
Old 04-30-19, 11:27 AM
  #25  
prj71
Senior Member
 
Join Date: Jun 2015
Location: North Central Wisconsin
Posts: 4,601
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 2965 Post(s)
Liked 1,167 Times in 763 Posts
Originally Posted by Kapusta
I understand what you are saying, and what I am saying is that it is not true. You are giving out bad advice, based on bad assumptions. Without knowing someones weight and tire size, you have NO IDEA what the optimum tire pressure is, and you had absolutely no basis to say that 30 was too high for the OP. You were shooting blindfolded in the dark. The range that "most people" run (which are numbers you are just making up based on almost no data), regardless of weight or tire size is utterly meaningless to any individual trying to get an of what pressure to run or even where to start. 30 PSI is ABSOLUTELY withing the range that some people end up. You just heard from a several in this thread. Were I running 2.1-2.2 tubed, I would be around 30, if not a little more.

And you are wrong about what the trade-off is. In mountain biking, it is not rolling resistance vs traction: The primary drivers are traction vs pinch flats and loss of stability, which means that you may need to run higher pressure in rougher terrain and for more aggressive riding. Look at what most DH or Enduro racers are running: 2.3-2.5 tubeless tires, with sturdy sidewall. Visit some forums and look at the pressures they are running: mid 20s to low 30s is typical. Some higher.

The proper advice was given elsewhere in this thread: start high, and slowly lower until you find where you are either getting pinch flats or tires squirming.
I never specified what the optimum is. I stated that early on this thread.

However I do know 30psi + is too much for the normal mountain biker riding single track trail system.

Some of you are overthinking this and it's rare that pinch flatting is an issue these days with the wheel, tire, tube combinations now available and isn't an issue at all if tubeless...which I am on the fat bike and my full suspension bike.

Last edited by prj71; 04-30-19 at 11:31 AM.
prj71 is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.