PSI for CX?

Anything and everything about cyclocross.

PSI for CX?

Postby kaysee » October 20th, 2017, 1:08 pm

First year racing on a true CX bike. I have no idea where to start for PSI.

I have tubes for now and weigh a little over 200. What ball park should I be in to avoid any potential pinch flats?
kaysee
 
Posts: 219
Joined: May 10th, 2011, 1:50 pm
Location: Royal Oak

Re: PSI for CX?

Postby MudAndCowbells » October 20th, 2017, 4:58 pm

Go ride (MTB trail or an actual warmup lap at a CX race) with your psi at 36. It you don't hit the rim at least once, you have too much air. Bottom out a ton, add more from there.
MudAndCowbells
 
Posts: 14
Joined: December 29th, 2015, 9:45 am

Re: PSI for CX?

Postby bikerector » October 22nd, 2017, 11:38 am

I would start with something like 35-40 front and 40-45 rear. A lot depends on the tire and width. I used to be a fan of as low of a pressure as could be tolerated before hitting rim but now I only apply that to really wet conditions where there's little firm footings in corners. If it's dry and you're running massively low pressure then you lose tire stability in hard corners. I've also had front tires give a sort of wash-out feeling when during hard up-and-overs where you come down hard on the front.

For dry weather I usually aim for something that will slightly "walk" when cornering on dry pavement at moderate speed which means it should be good for grassy and mildly soft corners.

No matter what pressure you run, you compromise somewhere on the course. Figure out where you struggle the most and prepare for that. Crashing is far slower than riding a little slower so you really want to prevent that. Especially being new on a CX bike, over-treading isn't a bad idea (skip the semi-slicks). I know a lot of people that simple run mud tread all year long.
"Life is what we make it"
http://www.cyclingandsuffering.com
User avatar
bikerector
 
Posts: 285
Joined: August 3rd, 2012, 8:03 am
Location: Wixom, MI

Re: PSI for CX?

Postby Rickwetherald » October 22nd, 2017, 12:32 pm

I'm not sure bottoming out the rim at least once is the best idea if you're running tubes. 1-2 rim strikes per lap, over the course of a full cx race will almost certainly result in at least one flat. Tubeless and tubular setups will be a different story, but at 200lbs and new to cx, I'd err higher than 36psi. Certainly, you'll hear of folks running much lower; light, smooth guys with a pit full of spare tubular wheels and bikes will run down into the low 20s or even high teens.

Poll lots of people and see what everyone is running at any particular race. If you're not sure, go higher. During the race, consider if it would be faster if you had lower pressure. Keep dropping in training and racing until you start having an issue with flats, than go back up.

Higher volume tires can run lower pressure.
Rockier/rootier courses or places that have on/off concrete shelfs that can pinch tubes require higher pressure.
Heavier riders require higher pressure.
Riders that are adept at floating or unweighting the bike over rough stuff can run lower pressure.

Add all that together in your head and you can get an idea of where you should be relative to everyone else.
Rick Wetherald -
Physical Therapy Clinic Director, Advanced Physical Therapy
Elite Coach & Bike Fitter, Athletes on Track Coaching
Rickwetherald
 
Posts: 119
Joined: July 20th, 2015, 10:56 am
Location: Wyandotte, MI

Re: PSI for CX?

Postby 3d » October 23rd, 2017, 10:19 am

I'm just shy of 200lbs and run about 35front-40rear on my 35mm tubed tires. At that I only bottom out if there are any hard roots (ann arbor) or curbs (mad anthony), but am good once i know where those hard points are. Given the choice though, I'd rather run stiff pizza cutters than wash out in the corners like mentioned above. Also like mentioned above, I run one tire all year, all conditions, and have no delusions of ever being a file tread tire or a few psi away from the podium :D
in it to ride, not to accessorize.
3d
 
Posts: 570
Joined: May 31st, 2005, 9:24 am
Location: detroit proper

Re: PSI for CX?

Postby kaysee » October 23rd, 2017, 10:47 am

I started a little closer to 45/45. Definitely didn't have trouble bottoming out at that rate. I haven't decided if I would have been able to corner any better on most of that course had I gone any lower anyway, maybe the two switchbacks towards the back of the park by the houses. But I'll drop it down a little more this weekend and see how it goes.

Also hoping to get these set up Tubeless, but I haven't investigated what the rim tape/strip situation is like in these wheels yet.
kaysee
 
Posts: 219
Joined: May 10th, 2011, 1:50 pm
Location: Royal Oak

Re: PSI for CX?

Postby Rickwetherald » October 23rd, 2017, 12:14 pm

kaysee wrote:Also hoping to get these set up Tubeless, but I haven't investigated what the rim tape/strip situation is like in these wheels yet.


Remember that lowering pressure doesn't just have advantages in corners; it really smooths out the bumpy pedaling sections. That Vet's Park course was fairly bumpy. I raced the P123 race on my geared bike with 40s at 28/30, and the difference was immense compared to my single speed with 33s at 32/33. That super slippery off-camber at the top was almost easier on the SS because it has mud tires compared to the geared bike's more minimal tread. The take-home here is to not rely just on cornering speed for ideal pressure decisions.

What kind of tires/rims are you on? I've been running tubeless for CX for about 3 years now and will never bother going back to tubulars, and will definitely avoid tubes whenever possible.
Rick Wetherald -
Physical Therapy Clinic Director, Advanced Physical Therapy
Elite Coach & Bike Fitter, Athletes on Track Coaching
Rickwetherald
 
Posts: 119
Joined: July 20th, 2015, 10:56 am
Location: Wyandotte, MI

Re: PSI for CX?

Postby kaysee » October 23rd, 2017, 12:57 pm

Rickwetherald wrote:
kaysee wrote:Also hoping to get these set up Tubeless, but I haven't investigated what the rim tape/strip situation is like in these wheels yet.


What kind of tires/rims are you on? I've been running tubeless for CX for about 3 years now and will never bother going back to tubulars, and will definitely avoid tubes whenever possible.


I'm on weinmann impulse TL doublewall rims and clement mxp tires. They should be good to go for a tubeless set up, I just haven't looked to see if I need to add any tape to the rim or not yet.
kaysee
 
Posts: 219
Joined: May 10th, 2011, 1:50 pm
Location: Royal Oak

Re: PSI for CX?

Postby Rickwetherald » October 23rd, 2017, 1:28 pm

Not sure on those. Does the 'TL' part imply tubeless compatibility?

I have no first hand experience, but have heard that Clement's tires don't always convert well. You might consider a Stan's rim strip or the ghetto-tubeless method (aka split tube method). I've also had better luck using Orange Seal sealant because it dries with more of a solid latex layer that sort of glues the sidewall to the rim.

I know some people complain about the hassle of converting to tubeless, but if it's done right it is totally worth it. In the long run, look for 35-40mm tubeless compatible tires. There are more and more on the market now, and I don't see any reason to run narrower if you're not constrained by the UCI rules.
Rick Wetherald -
Physical Therapy Clinic Director, Advanced Physical Therapy
Elite Coach & Bike Fitter, Athletes on Track Coaching
Rickwetherald
 
Posts: 119
Joined: July 20th, 2015, 10:56 am
Location: Wyandotte, MI


Return to Cyclocross

Who is online

Users browsing this forum: No registered users and 1 guest