akoubik

I purchased Trek Checkpoint SL5 in April this year and I really like it. The only problem I have is that the crank on the left side is so close to the frame that small gravel is getting between the crank and the frame and scratching the frame. Some of the scratches are pretty deep. I can see the carbon. The bike has only about 200 miles but all gravel. I am not sure what to do. I just don't think the film protector will help in this case.

tyrion

You could wrap a strip of inner tube around the chainstay, like people do on the drive side chainstay to protect it from the chain.

TiHabanero

If the crank arm is that close enough to the chain stay to cause gravel to get trapped and scratch the frame, check to see if the crank arm itself is hitting the frame when under load. Had this happen on a couple of builds using too short of a BB spindle.

TiHabanero

Hmmm, suspicious. For sure have the arm removed and the whole thing inspected by the shop. Never seen this before. Something is not right with that bike.

jfranci3

That has nothing to do with gravel

I'd say you're missing a seal or spacer. The Trek BB90 bottom bracket comes with a plastic tube. Maybe that's not on there. https://media.alltricks.com/hd/58fa09b19a475.jpg

Also the crank may not have been tightened in the right order. The 'barrel' bolt first, then then pinch bolts - https://www.parktool.com/blog/repair...ession-slotted . If you don't do this, the crank will move around.

The frame may also be out of spec.

delbiker1 

I am by no means an expert, but I have never seen a crank arm with so narrow of clearing. IMO, something is not right, or it is lousy engineering. Another 200 miles with that much damage and it is likely that will be dumpster material.

mstateglfr 

Buy yourself a bike with a threaded external bottom bracket.
Ride it.

Problem solved.



.All seriousness- that would be frustrating. Seems really counterintutitive to have a spinning item so close to the paint and layup.

jlaw

I looked for a NDS photo and found the one shown below. The clearance from the crank arm to the frame looks quite tight like yours, but I would still have a knowledgeable tech. check that your bike was assembled correctly.

Also, as shown in the bottom photo, you could install a bottle rack on the underside of the downtube with bottle or an improvised deflector to keep stones from the front wheel from reaching the area of the crank arm.

akoubik

Thank you for the replay. Yea I was thinking to put something on the arm to deflect the gravel from the frame but ... this is a $3K bike designed to ride in gravel. The terrain in the promo video Trek has online is about 10 worse than I do.

Roger Ramjet

I also have a Checkpoint SL5 like yours. I can confirm that the proximity of the crank arms to the frame appears to be normal.

That is unfortunate that Trek didn't catch that sort of thing in their testing. They did include carbon armor for the down tube and the drive side chainstay, looks like they need to think about BB shell armor, too.

I did drop the chain once on mine while shifting chainrings. I put vinyl tape (I used black) in the appropriate area to prevent any future scratching/damage.

bch238

You can get some 0.5 mm spacers from Wheels Mfg and put them between the NDS crank and the frame. I used two spacers (1.0 mm) to make some clearance between my 4iiii power meter crank arm and my chainstay on my Boone.

jfranci3

The .5 mm spacers are for the drive side to space the chainrings out. A wave washer would work better on the non-drive side and be lower fiction.

TXBDan

Interesting. I have an aluminum Checkpoint ALR5 and will have to to take a look for this. It probably has a simplier bottom bracket geometry, though. I have found that a Garmin cadence sensor will not fit between the crank and the frame. It's tight... :/

bch238

I don't see how friction is increased using spacers on NDS vs. DS. It seems sand and rocks abrading the frame, as OP reported, would create more friction than a spacer. The spacer is the same diameter as the face of the BB90 bracket, and is sandwiched between the bracket and the crank arm, moving as a single piece with both and the spindle. Anyway, I notice zero difference as far as friction goes. I don't necessarily agree that the spacers are designed exclusively for chainring alignment on DS, though they can be used for that. Using on NDS has no adverse effect, anyway. Whatever side you use them will effectively shorten the spindle length that the NDS crank can clamp to. And 1-2 mm will not compromise the crank clamping ability.

jfranci3

You're probably right. Here are the shims - https://amzn.to/3430onz It looks like they do have some spacing built in to reduce friction and are made out of delrin, so they'll be low friction in any case.

Note: I have the same bike and haven't had any paint issues. I'm using SRAM carbon crank with a BBinfinite GXP bottom bracket setup, this has like 3-5mm of clearance. That spot is super hard to get the protective tape on, so I find spray chain wax (Muc-Off specifically) is a good substitute. It goes on white-yellow and is hard to get off. It's just thick enough and tenacious enough to work, while not attracting dust. Spray a bit of that on around the rear stays/BB and tight crank arm sports before a rough ride. The water bottle idea would only work for limited circumstances over the stock padding in that same area below the downtube.


The AL bikes have a lot more space. I'm surprised that you can't put the sensor on a BB86 frame - it doesn't have clearance in the middle of the arm? I haven't had any issues with my Emonda ALR or old Crockett -again both SRAM though. A speed/cadence sensor on the rear stay might make more sense here anyway as you'll be in the woods. I would recommend putting a downtube / BB protector on it.

cartman42

Same issue here, trek checkpoint sl5 2020, gravel trapped scratched my frame. Bad design.
Unfortunately this stupid forum won't let me upload photos.

shelbyfv

It's OK, we can visualize a scratch.

akoubik

Cartman42 Shortly after my post Trek took both bikes back and refunded our money. (One of the reason why I purchased Trek again and probably will in the future). It was just getting really bad. We have small granite gravel in NW and it was just the perfect storm. I was not going to be stuck with bikes that will just shred themselves eventually. We purchased the aluminum Checkpoints AL5's and we are loving them. Yea the ride is not as smooth but the durability is there. After year of grave riding only there is not a scratch on them. Okay they need wash but other than that they are like new We changed the wheels for GRX. We love the frames so much we will update to GRX groupset when it become available again for more gearing. The 105 groupset is great but we live in the mountains we need gears. If Trek would not take them back, my idea was to put thinner stainless steel selfadhisive sheet metal between the frame and the crank. It would provide some protection to the carbon fiber frame around the bracket. Or just upgrade to GRX. The new SL5's have GRX have like 10 mm gap between the crank and the frame. I am sure SRAM have similar product.

akoubik

That is a pretty cheap comment.

seinberg 

FWIW, on my Checkpoint SL7 it seems fine. Maybe because the Force crank leaves more room? I also can't upload a picture or I'd show the clearance

akoubik

It is only the Shimano 105 (and probably Ultegra) road cranks. I think at the time when this bike was released it was the only groupset available. The 2021 Checkpoints have GRX. The gap between the frame and the crank is good.

mstateglfr 

I guess if Praxis Zayante, Praxis Alba, Easton, and a couple of quality FSA cranks all had the same design issue, then your explanation makes sense.

Toespeas

dont fall for treks BS , trek is one of the worst companies out , they mass produce garbage and sell it to people with more cash than knowledge , take it back to the DEALER posing as a bike shop , that you got it from , and make sure its right , if its right , send it back , find a better model , my buddies checkpoint cracked in half , they are terrible bikes with low quality material , so many better options for gavel , not to mention 3k for a gravel bike defeats the purpose of gravel riding , its suppose to be a bang for buck ride , cheap and easy , accessible to more people because you can use just about anything !

shelbyfv

Good to know! I wasn't aware of that

seinberg 

Where's the laugh emoji? oh, here it is!