Cyclocross and Gravelbiking (Recreational) This has to be the most physically intense sport ever invented. It's high speed bicycle racing on a short off road course or riding the off pavement rides on gravel like :The Dirty Kanza". We also have a dedicated Racing forum for the Cyclocross Hard Core Racers.

700x38 - is it enough?

Old 05-12-19, 06:44 PM
  #26  
Hiro11
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I did a 65 mile gravel race earlier this year on a single speed with slick 32s. A 40 up front and a 38 out back is actually a great setup.
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Old 05-13-19, 06:59 AM
  #27  
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Originally Posted by u235 View Post
I did two of the same centuries with two different tires a week apart. A route of about 50% gravel/trail and 50% paved. Hutchinson Overide 38 and new too me WTB Riddler 45. Both have pros and cons and the times/effort between them was dictated by the wind direction, not the difference in tires. I did the C&O/GAP last year with the Override. This year will be with the Riddler. I have multiple wheels sets and swap around because it is easy to do so I don't have to pick just one tire. My "gravel" bike is also a fire road bike, road bike, and a touring bike. More often than not in the same ride. There are people that do the same with a 28 or 32 and are perfectly happy. I have no idea how but....
How do those 45 riddlers roll on pavement compared to the Hutchinson Overide 38's?
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Old 05-13-19, 08:43 AM
  #28  
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Originally Posted by D-Fuzz View Post
With regards to the staggered sizes from front to back, is it important for each tire to be of similar tread type or can they be different?
38 rear 40 front works great for me - I can't really tell the difference between the two (even looking at them side by side) other than the frame clearance.

I like slicks (or near slicks) on the rear, and change the tread and size of the front tire for the conditions.

I often leave my rear tire alone and change my front tire for the riding conditions.
28mm for fast pace line (slick)
32mm for general hard pack summer riding (slick)
40mm for extended gravel and winter/spring ridng (smaller gravel knobs)
50mm for soft sandy rides where I need the flotation, or when I throw in some single track. (medium knobs)
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Old 05-13-19, 10:27 AM
  #29  
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Originally Posted by Hmmm View Post
How do those 45 riddlers roll on pavement compared to the Hutchinson Overide 38's?
It's actually not too bad but the Overide is faster. I run the Override at 45/55, the Riddlers at 35/40. In the 300 or so miles I put on them so far about 150 has been on some type of pavement. More than the actual rolling resistance difference is the handling, immediately after switching I can feel the Riddler is a little more sloppy on the road as expected, after a mile or so that difference goes away as I adjust. Another is the "bounce" of the Riddler. Specially out of the saddle, again expected. On the flip side, even in smooth gravel, the Riddler was better overall in comfort, traction, and perceived effort. In my back to back mixed centuries I did to compare.. The Overide average speed was 14.5 and the Riddler was 15.2. You could take those results out of context and come to the wrong conclusion. I had a terrible direct head wind on the last 25 or so miles of the road portion on the trip with the Overide. I wouldn't suggest the Riddler as a road tire but it can do large gaps of road between gravel with no problem and it more than makes up for it off road, even smooth gravel. For me the decision comes down to a lot of my gravel rides include some type of rough and random patches of washout with mud and peanut butter and the slickness of the Overide is weak there. Sure I can hang on to go straight through those and I have but I want a larger volume and some tread. I don't mind looking ahead and picking my lines but hour upon hour of that compensating for what is effectively a slick gets old. With the Riddler I have some flexibility and can pay less attention

Last edited by u235; 05-13-19 at 12:10 PM.
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Old 05-13-19, 11:30 AM
  #30  
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Iíve decided to run a 40 Kenda Happy Medium on the front and a 38 Specialized Trigger Pro on the rear. I am about 2 minutes from the edge of the city and thousands of kms of gravel roads, so my pavement riding with this bike will be minimal.
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Old 05-13-19, 02:24 PM
  #31  
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That will work. Enjoy!!!
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Old 05-13-19, 02:38 PM
  #32  
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Originally Posted by D-Fuzz View Post
I just finished a 70km ride with a friend who is riding with 42mm Sawtooths. For most of the ride there was very little difference between us until we got a stretch with thick pea gravel about 3-4 inches deep. He was able to handle quite a bit easier than me. I felt like I was pedalling and not getting anywhere. Overall I was pretty pleased with how the bike felt and performed though.
The thing with the Sawtooth 42s...they're very heavy tires. Very durable and long-wearing. But heavy. IIRC each tire is 600gram each. There are other semi-slick tires (Vittoria, Compass/Rene-Herse/Panaracer) with more grip for say cornering that weigh 30% (read half-a-pound less per tire).
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Old 05-19-19, 10:06 PM
  #33  
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I did another 80+km ride today with the bike and it doesnít seem like the tires are much of a limiting factor. There are times when the gravel gets pretty thick (3-4 inch deep pea gravel) and it is a bit of a grind, but in pretty much every other condition the bike handles well and rides nicely. I am still running tubes (38 front/40 rear) but I might switch over to tubeless, we will see.
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Old 05-19-19, 10:09 PM
  #34  
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Racing cyclocross, UCI limit is 33 mm ..
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Old 05-23-19, 08:39 PM
  #35  
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Originally Posted by ksryder View Post
The smaller tire in back thing -- some people do that for mud clearance. I don't, because it usually doesn't rain that much where I live and I avoid riding in the mud if possible.
It is also a question of having the wider tire in front. All other things being equal, wider tire = better grip. When cornering, it is preferable to have the rear tire to skid first, not the front one
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Old 05-23-19, 08:48 PM
  #36  
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Personally, I would be concerned about the volume of the tire. For gravel, I would think you’d want higher volume tires with more cushiness in them and lower tire pressures. Just seems like a 700x38 wouldn’t take up as much volume. I have some 700x32 Continental Grand Prix 5000 and they don’t have much volume at all. Very firm and have to be pumped to at least 70 PSI. Just can’t see anything on a 700c tire having enough volume to allow for PSI’s as low as 35 to 40. That just doesn’t seem possible. Maybe I’m wrong though.

I ended up getting a 650b wheel set with some WTB Horizon’s. Now, those do indeed allow for lower pressures and are cushy as all get out. Plus, the extra space allows for a deeper profile tire that ends up being about the same circumference as a 700c tire. Really enjoy the feel of my rides with them.
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Old 05-23-19, 08:56 PM
  #37  
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Originally Posted by srode1 View Post
Depends on what kind of gravel you are riding, how much you weigh and how fast you want to go plus other factors. Michigan fire trails as an example have quite a bit of sand and bigger tires are great in that environment, 45mm would a good choice if you don't want to get off and walk as much. B-roads with ruts and big gravel I want 40mm or larger. Regular dual lane A gravel roads that have fine gravel sub 40mm works well.
I'll add to this that it seems like tire size may have a direct relationship to the size of loose gravel you are riding on. My gut says if the loose gravel is x mm in diameter, you want your tires to be 1.5x mm.
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Old 05-23-19, 09:46 PM
  #38  
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I did another ride last night with my
friends running 700x45 and 650x47 tires. The only real difference I found was I needed to be a bit more aware of my lines when riding in heavy, deep gravel. Those guys seemed to glide over gravel ridges where I needed to take them at a bit more of an angle. The more I ride the bike, the more comfortable I get with how it handles.
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Old 05-23-19, 09:58 PM
  #39  
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Originally Posted by D-Fuzz View Post
I did another ride last night with my
friends running 700x45 and 650x47 tires. The only real difference I found was I needed to be a bit more aware of my lines when riding in heavy, deep gravel. Those guys seemed to glide over gravel ridges where I needed to take them at a bit more of an angle. The more I ride the bike, the more comfortable I get with how it handles.
Based on what Iíve read when researching gravel tires, the big difference between a 700c and a 650b tire is the volume. Considering thereís at least an inch difference in the wheel sizes, a 650b tire will give you more volume since the tire has to have a bit larger profile to provide the same overall wheel size as a 700c. So, yeah, wouldnít surprise me in the least that a 650x47 will provide more control over a 700x45. Iím running on 47ís myself and love them. The extra flex in the tire does indeed allow for more glide over rougher surfaces, thus the reason why the 650b wheel size is becoming so popular. Not sure how much of a difference it makes with speed though. Personally, I prefer a smoother ride with more control.
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Old 05-23-19, 10:06 PM
  #40  
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I contacted Felt to ask whether 650b wheels will work with my bike. They said they will, so I might give them a test fit to see how that goes.
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Old 05-24-19, 05:07 AM
  #41  
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Originally Posted by jeffwhitfield View Post
Based on what Iíve read when researching gravel tires, the big difference between a 700c and a 650b tire is the volume. Considering thereís at least an inch difference in the wheel sizes, a 650b tire will give you more volume since the tire has to have a bit larger profile to provide the same overall wheel size as a 700c. So, yeah, wouldnít surprise me in the least that a 650x47 will provide more control over a 700x45. Iím running on 47ís myself and love them. The extra flex in the tire does indeed allow for more glide over rougher surfaces, thus the reason why the 650b wheel size is becoming so popular. Not sure how much of a difference it makes with speed though. Personally, I prefer a smoother ride with more control.
Just to note that a 700c 45mm has a larger diameter than a 650b 47mm. 650b 47mm is roughly the same diameter as a 700c 28mm. It is interesting because you can change between wheels for road and gravel without affecting the geometry of the bike. If the bike can take both wheels and has enough tire clearance.

Last edited by fraba; 05-24-19 at 05:11 AM.
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Old 05-24-19, 08:49 AM
  #42  
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Originally Posted by jeffwhitfield View Post
Just canít see anything on a 700c tire having enough volume to allow for PSIís as low as 35 to 40. That just doesnít seem possible. Maybe Iím wrong though.
Yes, you are. I'm running my 37 mm tires (real width on my rims is 39 mm) at 35 PSI front, 42 back. With tubes.
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Old 05-24-19, 09:20 AM
  #43  
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Originally Posted by fraba View Post
Just to note that a 700c 45mm has a larger diameter than a 650b 47mm. 650b 47mm is roughly the same diameter as a 700c 28mm. It is interesting because you can change between wheels for road and gravel without affecting the geometry of the bike. If the bike can take both wheels and has enough tire clearance.
Gah, I'm dumb. I didn't even think about that. That totally explains the popularity of the 650b wheel set. No way can I put a 700c 45mm tire on my bike...won't have the clearance.
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Old 05-24-19, 10:00 AM
  #44  
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+1 for 38's being more than enough, I also run Hutchinson Overides and although they are a bit of a compromise (more of an "all-road" tyre than gravel) they are perfect for dry gravel and trails and they don't feel sluggish on road.

I've used my Overides on everything, road, bridleways, forest tracks and even some MTB trails and I've never felt like I'm at a disadvantage. I feel like 38mm is the sweet spot for tyres, obviously a wider tyre has its benefits but if you're just using a single wheelset then you can do a lot worse than sticking with 38s.

Last edited by RicePudding; 05-24-19 at 10:27 AM.
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Old 05-24-19, 02:16 PM
  #45  
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Trigger Pros are such a great tire.
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Old 05-24-19, 03:41 PM
  #46  
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I’m gonna have to remember 38’s the next time I switch out my 650b tires. I’m running on 47’s, which are great, but if 38’s are a little better then I’ll try that.
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Old 05-25-19, 09:44 PM
  #47  
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Originally Posted by jeffwhitfield View Post
Just can’t see anything on a 700c tire having enough volume to allow for PSI’s as low as 35 to 40. That just doesn’t seem possible. Maybe I’m wrong though.
The 40mm Clemente explore MSO's take 35-55 psi tubeless. I run mine at 40psi for comfort and traction. At 55 psi I do not get as good traction as 40psi.
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Old 06-10-19, 09:18 AM
  #48  
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Originally Posted by Gconan View Post
The 40mm Clemente explore MSO's take 35-55 psi tubeless. I run mine at 40psi for comfort and traction. At 55 psi I do not get as good traction as 40psi.
I'm new to gravel and tubeless, but just ran my 40mm Giant Crosscuts at 40psi front/50psi rear and they performed great! Had no issues at all on a ride that was mostly gravel, some singletrack, bit of wet sand/mud, and some pavement where I had no problems holding 20+mph. Absolutely loving the tubeless, comfort and handling/traction were great.
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Old 06-10-19, 12:08 PM
  #49  
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Originally Posted by Rides4Beer View Post
I'm new to gravel and tubeless, but just ran my 40mm Giant Crosscuts at 40psi front/50psi rear and they performed great! Had no issues at all on a ride that was mostly gravel, some singletrack, bit of wet sand/mud, and some pavement where I had no problems holding 20+mph. Absolutely loving the tubeless, comfort and handling/traction were great.
Those pressures are a bit high for a 40mm tubeless tire. Might want to drop to, say, 35f/40r and see how it feels.

For what it's worth, I've run my 37mm tires as low as 25f/28r. At that pressure, the rear tire gets a little squirmy through corners, but still feels pretty fast.
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Old 06-10-19, 12:35 PM
  #50  
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Originally Posted by Koyote View Post
Those pressures are a bit high for a 40mm tubeless tire. Might want to drop to, say, 35f/40r and see how it feels.

For what it's worth, I've run my 37mm tires as low as 25f/28r. At that pressure, the rear tire gets a little squirmy through corners, but still feels pretty fast.
I would think it also depends on the weight of the rider. That was my first gravel ride, I'm 185lbs and didn't want to go too low to start with. Guy at my LBS is about my size and rides at 40psi, so I figured it would be a good starting point, it worked really well for that ride.
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