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Carbon rims and tire pressure


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I'm new to the world of carbon rims, and I recently cracked my month old rear rim on a moderate drop.  I was running about 20 PSI with a 29X3 tire, which from everything I can tell is relatively high for someone who weighs less than 160lbs.  In fact, at that pressure, I felt like climbing traction is merely very good, but not out of this world as one might expect from the 29+ format.  As I look to replace the rim (hopefully covered by warranty), I find myself thinking more about tire pressure than I ever have before - particularly since I had previously never even dented a rim running low enough pressure to get the occasional rim strkes. 

Those of you running carbon rims, do you find that you have to run them at higher than normal pressure to guard against rim failure riding the local trails?  Prior to this failure, I was really enjoying the carbon rims, but if I need to run them at higher pressure levels, I guess I will be a jackass, unhappy with another first world problem.

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im also on my first set of carbon wheels and honestly dont feel/notice the benefits. quite the opposite rather. im always paranoid about breaking them, running Cush core and dealing with the complications/hassles of that, blah blah blah. and the weight savings are minimal if non existent. I probably wouldnt hesitate a minute to sell them and get the new Stans flow EX3 rims.

 

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I'm running 27.5  x 2.6 Rekons on Santa Cruz R37 rims with HuckNorris. I am murder on rims, but I haven't felt a significant rim strike in 1000 miles. I've had a few small ones, but no rim dings and no pinch flats, which is huge for me.  I also haven't so much as tightened up a spoke.

 

Historically I run 28-30psi on 2.4 and 2.5 Minions and rim dings and pinch flat like mad.

Lately:

 

Walnut: 17-18 psi.

Brushy and BCGB: 21-23 psi.

Goodwater: 23-24 psi (but it was an all out pace)

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Nope, nothing of the sort here.  I'm 165lbs running 13.5 lbs (rear) on my 3" XR2s and have had no problems.  I've done a few of the smaller drops over near basket(?) on Picnic (on my hardtail) too.  Additionally, I've ridden/raced the Dragon Slayer on same bike/wheels too.

In fact just 2 days ago, I had the rear tire off for the first time and checked trueness and for abrasions and they're in perfect condition.

How wide are yours?

-CJB

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I'm on carbon hoops Nextie for about a year now with no issues granted I don't ride like Seth does but at 235# on 28 hole hoops you would think I would have had an issue by now. Some of your issue may be due to the tires you're running. I just switched to Maxxis tires and OMG they are stiff and harsh at the same pressures I was running my Schwalbes. The Schwalbes were way more supple but the Maxxis would definitely help protect the rim in contact situation. What carbon hoops do you have?

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4 hours ago, Seths Pool said:

im also on my first set of carbon wheels and honestly dont feel/notice the benefits. quite the opposite rather. im always paranoid about breaking them, running Cush core and dealing with the complications/hassles of that, blah blah blah. and the weight savings are minimal if non existent. I probably wouldnt hesitate a minute to sell them and get the new Stans flow EX3 rims.

 

This^

Im on a set of M70HV enves and they've been nothing but trouble. Hard to seal, ride rough AF, expensive, not that light, and make you paranoid. To do over I'd buy a set of DT swiss aluminum in a heartbeat.

 

O.P. What rims are you running? That seems pretty fragile for a 3" tire and weighing 160lbs.

Edited by ATXZJ
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22 minutes ago, ATXZJ said:

This^

Im on a set of M70HV enves and they've beem nothing but trouble. Hard to seal, ride rough AF, expensive and make you paranoid. To do over I'd buy a set of DT swiss aluminum in a heartbeat.

 

O.P. What rims are you running? That seems pretty fragile for a 3" tire and weighing 160lbs.

Thats why I went with Chi-carbon all-in for $750 (including DT350's).  I figured that even if I trash a rim, I could replace it again for $200 and still be in at a reasonable price.  I'm historically pretty easy on wheels, but that doesn't mean that they see an easy life.  I bet I've made over 100 miles of LGT on them.  And thats not been a Sunday stroll through the flowers....

But I do agree that if I was a bigger dude doing more hucking stuff, the new Stan's Flow seems like a winner.

-CJB

Edited by CBaron
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Thanks for the feedback.  I am running Bontrager Line Pro 40s with XR2 (Chupacabra) tires.  I believe that the rims are internally 41mm wide.  The drop that caused the crack is the EBD at Brushy.  The thing is I usually take the same setup and take it down the bigger Picnic X drop and the Basket drop and haven't felt anything odd.  Even when the rim cracked, the tire remained intact (no pinch flat), which to me seems to suggest that the impact wasn't all that significant.  I won't do anything crazy, but I like to ride all the drops I encounter at City Park and Brushy.  I assumed that this setup would be fine for this type of riding, particularly given my weight, but is that a poor assumption?  

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10 hours ago, Cafeend said:

Anyone running Dirt Component wheels?

Interested in these guys as well.  They're literally down the street.

Carbon that close to the rocks doesn't do it for me.  I've bent up aluminum rims and they've never catastrophically failed and sent me OTB.  If a carbon rim fails, it seems like it will really fail and you're walking/limping out.  When I got my first carbon frame, I was worried about laying it over on a rock and breaking the stupid thing where my old Al frame would have just got a nick.  After time, I crashed a few times and the frame held up so I stopped thinking about it.  I'd love to have a pair of carbon rims and not think about them during a ride but I'm not convinced that the tech is there yet and I'd rather take that money and buy more parts.

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I'm running second-hand Knox.  The previous owner was about 170 and does all the drops jumps, etc..  I'm about 220 all geared up.   I roll down stuff, huck off small stuff and bomb down St. Eds and frequently get rock strikes on the wheels (they have plenty of chips on the clearcoat).  So far so good.  They are definitely lighter and stiffer than what I could get something equivalent in aluminum.

Edited by AntonioGG
Forgot to add, I run 20-25psi front and 22-28psi rear. Usually prefer more pressure on the smooth and hard cornering trails.
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12 hours ago, Cafeend said:

Anyone running Dirt Component wheels?

Sent from my SM-N960U using Tapatalk
 

I have been riding a set of 29 carbon Dirt wheels for 3-4 months, and I am a big fan already.  I am 195 lbs and I drop everything at Brushy often.  I love them.  I ride with alot more pressure than you guys though...30psi.  

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16 hours ago, CBaron said:

Thats why I went with Chi-carbon all-in for $750 (including DT350's).  I figured that even if I trash a rim, I could replace it again for $200 and still be in at a reasonable price.  I'm historically pretty easy on wheels, but that doesn't mean that they see an easy life.  I bet I've made over 100 miles of LGT on them.  And thats not been a Sunday stroll through the flowers....

But I do agree that if I was a bigger dude doing more hucking stuff, the new Stan's Flow seems like a winner.

-CJB

Which Chi carbon are you using? I was looking at Farsport, having build up a bunch of their rims for road wheels.

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3 minutes ago, Mattlikesbikes said:

Which Chi carbon are you using? I was looking at Farsport, having build up a bunch of their rims for road wheels.

EIE Carbon.  I found them because they offered a i39 rim that was lightweight.  It was the only rim of that width-weight-price I could locate.  My goal was to have something I could run 3" primarily....but also stretch some 2.6's onto for a racing setup.  They've been a great purchase, I have no regrets.  And they came in almost uncomfortably light for me (1650 grams!).  The only issue for me so far is that I'm having a hard time locating a tire in the 2.6 realm that is significantly lighter than my 3" XR2s....

http://www.eiecarbon.com

-CJB

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6 hours ago, Haught Diggity said:

I have been riding a set of 29 carbon Dirt wheels for 3-4 months, and I am a big fan already.  I am 195 lbs and I drop everything at Brushy often.  I love them.  I ride with alot more pressure than you guys though...30psi.  

30psi will definitely protect your carbon hoops. But depending on your tire choice 30psi might not be the best ride or handling. I had Schwalbe tires previously, a new version Hans Dampf 29x2.35 front and a Nobby Nic 29x2.35 rear on 29mm IW hoops. I was running 28 psi rear and 23 front. Tires felt good and handled well at those pressures without rim strikes. Switched to Maxxis DHF 29x2.5 front and Aggressor 29x2.5 rear. Aired these tires up to the same pressures I was running in the Schwalbe's. They felt like I had 45-50psi in them. The carcass is much stiffer in these tires than the Schwalbe's they felt like solid rubber tires. I aired the Maxxis down to 20psi rear and 15 front and they feel pretty good now I may be able to go a bit lower, but at these lower pressures no rim strikes at all. So air pressure is going to give different results between different tire brands. BTW I really like the Aggressor on the back, almost enough to consider it for the front.

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Just got a set of bontrager line comp 30 aluminum rims from rei for $260 (sale price) to try on my hard tail.   I have these rims on my fuel and they've handled a few hundred miles of Lake Georgetown,  Deception and RPR without any issues.   They aren't light but they're strong.  My riding weight is about 230 so weight isn't much of a factor for me.   Might be a good backup set to have around. 

 

Also tried out the new Specialized Eliminator Black Diamond 2.6 as a front tire.  It's got a really thick sidewall so I'm thinking I'll need to lower the pressure to maybe about 20-21 psi. Noticeably heavier than my 2.4 xr4, but I dont mind.  Lake Georgetown slashed my xr4 so I was looking for tougher sidewalls. 

 

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12 hours ago, JRIDER said:

Just got a set of bontrager line comp 30 aluminum rims from rei for $260 (sale price) to try on my hard tail.   I have these rims on my fuel and they've handled a few hundred miles of Lake Georgetown,  Deception and RPR without any issues.   They aren't light but they're strong.  My riding weight is about 230 so weight isn't much of a factor for me.   Might be a good backup set to have around. 

My Trek Remedy 9.8 came with the Bontrager Line Elite 30 wheels, and I bent the rear rim in 2 places after around 4 rides out at Brushy. I'm getting it replaced with the same rim and will try to be more careful with my tire pressures. I'm around 192lbs riding weight and normally run around 26psi in the rear. Admittedly when the dings occurred I may have failed to recheck my tire pressures before heading out, but that's not unusual for me and has never led to problems with the DT Swiss XMC 1200 24mm internal carbon rims on my other bike. I'm thinking that those wider Line Elite 30 rims need a wider tire than the 2.4s that came on it. I'll probably put some 2.6 tires on it front and back before I start doing too much on it again. 

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