Go Back  Bike Forums > The Racer's Forum > Cyclocross Racing
Reload this Page >

Tire Pressure Question

Cyclocross Racing Discuss pro racing, the big races, and even the small backyard races. Don't forget to update all the members with your own race results.

Tire Pressure Question

Old 09-26-18, 11:50 AM
  #1  
Abe_Froman
Senior Member
Thread Starter
 
Abe_Froman's Avatar
 
Join Date: Aug 2016
Location: Chicago
Posts: 2,533

Bikes: Marin Four Corners, 1960's Schwinn Racer in middle of restoration, mid 70s Motobecane Grand Touring, various other heaps.

Mentioned: 75 Post(s)
Tagged: 0 Thread(s)
Quoted: 9291 Post(s)
Liked 42 Times in 36 Posts
Tire Pressure Question

So, I've done a handful of races, and am still trying to figure out tire pressure. Running tubes currently. My question is this...SHOULD the tire be folding over/deforming in a corner, or is this something to avoid? My back tire has been deforming on harder corners. I've got it at 30psi right now. I'm thinkiing ~35psi or so might be more effective...but eh. Figured I'd have the community weight in.
Abe_Froman is offline  
Old 09-26-18, 12:12 PM
  #2  
wgscott
Occam's Rotor
 
wgscott's Avatar
 
Join Date: Jul 2013
Location: The Timbers of Fennario (CL77)
Posts: 4,887

Bikes: Steel

Mentioned: 61 Post(s)
Tagged: 0 Thread(s)
Quoted: 2366 Post(s)
Liked 213 Times in 132 Posts
I'm no expert, but I would suggest it should not be folding. Deforming is normal. 35psi seems low unless they are quite wide (how wide?).
wgscott is offline  
Old 09-26-18, 12:42 PM
  #3  
ldmataya 
Senior Member
 
ldmataya's Avatar
 
Join Date: Jan 2009
Location: Mt. Horeb, Wisconsin
Posts: 489
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 53 Post(s)
Likes: 0
Liked 2 Times in 1 Post
Deforming - sure, but I'm not sure to what extent you think it is bad. When cornering hard at low pressure, you should feel the tire grabbing turf or even slipping out slightly, and you will feel the rim moving around a bit - all normal. But if it feels like a flat rear would feel on gentle cornering, where the rim is obviously moving a lot relative to the tire, then you probably don't have a high quality rim-tire combo if indeed you have 30psi in a 33c wide tire. When running tubeless I am at 24/26 front/rear and I weigh 155. 30-35 would feel rock hard and would be slower on bumpy ground. Pros running tubeless clinchers are in my ballpark, definitely lower if they are smaller than me. But they have high quality tubeless setups (where the bead pops on with a loud snap as you inflate them). Occasionally I've had to stick a tube into my tubleless setup, I keep it at 26 and don't worry about pinch flats - its just a race.
ldmataya is offline  
Old 09-26-18, 12:58 PM
  #4  
KraneXL
 
KraneXL's Avatar
 
Join Date: Feb 2015
Location: La-la Land, CA
Posts: 3,174

Bikes: Cannondale Quick SL1 Bike - 2014

Mentioned: 25 Post(s)
Tagged: 0 Thread(s)
Quoted: 2812 Post(s)
Liked 64 Times in 54 Posts
Originally Posted by Abe_Froman View Post
So, I've done a handful of races, and am still trying to figure out tire pressure. Running tubes currently. My question is this...SHOULD the tire be folding over/deforming in a corner, or is this something to avoid? My back tire has been deforming on harder corners. I've got it at 30psi right now. I'm thinkiing ~35psi or so might be more effective...but eh. Figured I'd have the community weight in.
Depends on the pressure rating, surface, type of tire, and weight of the rider (all of which you excluded). In all cases there is a range of acceptability according to the rider's preference.
KraneXL is offline  
Old 09-26-18, 01:12 PM
  #5  
Abe_Froman
Senior Member
Thread Starter
 
Abe_Froman's Avatar
 
Join Date: Aug 2016
Location: Chicago
Posts: 2,533

Bikes: Marin Four Corners, 1960's Schwinn Racer in middle of restoration, mid 70s Motobecane Grand Touring, various other heaps.

Mentioned: 75 Post(s)
Tagged: 0 Thread(s)
Quoted: 9291 Post(s)
Liked 42 Times in 36 Posts
Originally Posted by KraneXL View Post
Depends on the pressure rating, surface, type of tire, and weight of the rider (all of which you excluded). In all cases there is a range of acceptability according to the rider's preference.
Sorry. I'm 190lbs, on 35mm all purpose cross tires. No idea what the rating is...but I really doubt that makes any difference.

Thinking of getting a set of Compass Steilacoom tires and running them tubeless....but just worrying about tubed setup right now.
Abe_Froman is offline  
Old 09-26-18, 01:49 PM
  #6  
justin1138
Senior Member
 
justin1138's Avatar
 
Join Date: Apr 2013
Location: Portland, OR
Posts: 434

Bikes: yes...

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 43 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by Abe_Froman View Post
Sorry. I'm 190lbs, on 35mm all purpose cross tires.
Similar weight and tire set up, I have my pressure around 35#'s. The front is usually 1-2#'s lower than the rear.

I like to feel it out in the yard a day or two before racing (so there's no surprises), and add/subtract pressure so there's not too much rim hitting the ground.
justin1138 is online now  
Old 09-26-18, 02:36 PM
  #7  
Abe_Froman
Senior Member
Thread Starter
 
Abe_Froman's Avatar
 
Join Date: Aug 2016
Location: Chicago
Posts: 2,533

Bikes: Marin Four Corners, 1960's Schwinn Racer in middle of restoration, mid 70s Motobecane Grand Touring, various other heaps.

Mentioned: 75 Post(s)
Tagged: 0 Thread(s)
Quoted: 9291 Post(s)
Liked 42 Times in 36 Posts
Originally Posted by justin1138 View Post
Similar weight and tire set up, I have my pressure around 35#'s. The front is usually 1-2#'s lower than the rear.

I like to feel it out in the yard a day or two before racing (so there's no surprises), and add/subtract pressure so there's not too much rim hitting the ground.
Ok good to know. Yea the first race of the season I had the back at 35psi...and only noticed what I think was a foldover once, and it was on a very slight off camber that I took pretty hard. Then the next race I had it at 30...and it seemed I had that sensation on pretty much every corner I took hard.
Abe_Froman is offline  
Old 09-27-18, 06:27 AM
  #8  
Jakedatc
Senior Member
 
Jakedatc's Avatar
 
Join Date: Oct 2007
Location: CT
Posts: 3,028
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Originally Posted by Abe_Froman View Post
Sorry. I'm 190lbs, on 35mm all purpose cross tires. No idea what the rating is...but I really doubt that makes any difference.

Thinking of getting a set of Compass Steilacoom tires and running them tubeless....but just worrying about tubed setup right now.
Check out some Donnelly BOS or PDX if you want a good chunky CX tire for tubeless. https://www.probikekit.com/bicycle-t.../11651868.html

I also run 25ish on tubeless (125lb)
Jakedatc is offline  
Old 09-27-18, 10:54 AM
  #9  
redlude97
Senior Member
 
Join Date: Sep 2011
Posts: 4,190
Mentioned: 27 Post(s)
Tagged: 0 Thread(s)
Quoted: 1669 Post(s)
Liked 23 Times in 19 Posts
I generally check my pressures during the course previews by lowering it until they bottom out on the roughest sections and then adding back a few psi. Since you are running tubed that may not be an option. A good amount of squirm is normal though and you just get used to it if you are coming from a mostly road background
redlude97 is offline  
Old 09-27-18, 11:05 AM
  #10  
Abe_Froman
Senior Member
Thread Starter
 
Abe_Froman's Avatar
 
Join Date: Aug 2016
Location: Chicago
Posts: 2,533

Bikes: Marin Four Corners, 1960's Schwinn Racer in middle of restoration, mid 70s Motobecane Grand Touring, various other heaps.

Mentioned: 75 Post(s)
Tagged: 0 Thread(s)
Quoted: 9291 Post(s)
Liked 42 Times in 36 Posts
Originally Posted by redlude97 View Post
I generally check my pressures during the course previews by lowering it until they bottom out on the roughest sections and then adding back a few psi. Since you are running tubed that may not be an option. A good amount of squirm is normal though and you just get used to it if you are coming from a mostly road background
Well the squirm didnt phase me at all. But the tire folding completely over, the rim sliding sideways across it and onto the ground was a bit disconcerting lol.
Abe_Froman is offline  
Old 10-04-18, 10:45 AM
  #11  
50voltphantom
Senior Member
 
50voltphantom's Avatar
 
Join Date: Feb 2014
Location: SD
Posts: 2,661

Bikes: Handsome Fredward, Trek 1.1

Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 449 Post(s)
Liked 5 Times in 4 Posts
Originally Posted by Abe_Froman View Post
Well the squirm didnt phase me at all. But the tire folding completely over, the rim sliding sideways across it and onto the ground was a bit disconcerting lol.
More then. If it's affecting your line choice, adjustment is needed.
50voltphantom is offline  
Old 10-05-18, 08:15 AM
  #12  
Abe_Froman
Senior Member
Thread Starter
 
Abe_Froman's Avatar
 
Join Date: Aug 2016
Location: Chicago
Posts: 2,533

Bikes: Marin Four Corners, 1960's Schwinn Racer in middle of restoration, mid 70s Motobecane Grand Touring, various other heaps.

Mentioned: 75 Post(s)
Tagged: 0 Thread(s)
Quoted: 9291 Post(s)
Liked 42 Times in 36 Posts
Originally Posted by 50voltphantom View Post
More then. If it's affecting your line choice, adjustment is needed.
Yea. I've tried it at 34/36...feels much better.
Abe_Froman is offline  
Old 06-25-19, 12:57 PM
  #13  
tpower
Junior Member
 
Join Date: Jun 2019
Posts: 8
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 3 Times in 3 Posts
It doesn't sound like you have a very wide rim. Narrow rims with 35mm tires will fold over more easily. I had a stock rim I raced a few times as backup and it was really flexy and bouncy. I ran 35c tires at or around 32psi with tubes...would pinch flat going lower. For safety purposes I would personally shy away from completely folding the tire over like you're describing. This seems like an accident waiting to happen.

My philosophy is to run higher PSI than you think because if you flat you're essentially out of contention unless the pit is like right there.

So:
If running tubes, add PSI to avoid pinch flat
If running tubeless, consider adding to avoid burp if the course has a lot of off camber
If you run tubulars then go ahead and drop it lower. You can hit rim and get away with it.

I ran under 27psi or so all season on tubulars and those things hooked up so well. I can't imagine running under 20psi though like the pros in some of these muddy races.

Pre-ride and adjust accordingly but over here its very difficult to pre-ride at race speed so this strategy is hard to employ.

Also, keep a log of the course, conditions and PSI for future.
tpower is offline  
Old 06-25-19, 03:38 PM
  #14  
bbbean 
Senior Member
 
bbbean's Avatar
 
Join Date: Jul 2013
Location: Missouri
Posts: 2,063

Bikes: Giant Propel, Cannondale SuperX, Univega Alpina Ultima

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 319 Post(s)
Liked 27 Times in 22 Posts
Trial and error, varies by course and condition. You can run a lot lower pressure in the mud than on rocks and roots. Start at 35 and work your way down til you find the right feel for you.
__________________

Formerly fastest rider in the grupetto, currently slowest guy in the peloton

bbbean is offline  
Old 06-26-19, 07:58 AM
  #15  
50voltphantom
Senior Member
 
50voltphantom's Avatar
 
Join Date: Feb 2014
Location: SD
Posts: 2,661

Bikes: Handsome Fredward, Trek 1.1

Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 449 Post(s)
Liked 5 Times in 4 Posts
Originally Posted by bbbean View Post
Trial and error, varies by course and condition. You can run a lot lower pressure in the mud than on rocks and roots. Start at 35 and work your way down til you find the right feel for you.
Exactly. When it's really sloppy with minimal rocks/roots you can really get into silly territory with pressures. I was running <~20psi in the front and <30psi rear with tubes at the really wet races last year and I weigh about 195. As long as you're not experiencing understeer and can stay light on the bike you'll probably be ok. Yes I bottomed out my front tire a lot. My baseline is 22F/32R.
50voltphantom is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Andy_K
Cyclocross and Gravelbiking (Recreational)
0
02-11-13 04:48 PM
Siu Blue Wind
Foo
2
12-03-11 02:24 PM
superduper54
Singlespeed & Fixed Gear
8
07-03-09 01:48 PM
mirona
Road Cycling
752
08-26-06 04:49 AM
alwaysbefirst
Road Cycling
1
07-25-05 03:26 PM

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

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

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.