# 140mm Discs on 2020 Trek Domane?



## PoorInRichfield (Nov 30, 2013)

_Note: This question is coming from a lazy many who just doesn't want to start taking apart his new bike to answer his own question. You've been warned!_ 

My 2020 Trek Domane SL7 has 160mm disc rotors and I'm wondering if there would be any issue with going to 140mm discs. 

I know that in order to do this, the adapters/spacers that the calipers are currently mounted on would have to come off. What I'm not sure about is if there are mounting holes on both the fork and chain stay for direct-mounting the calipers w/o the spacers? It looks like the chain stay will be OK, but it's hard to tell if the fork only has bolt holes for the spacers or not.

The reason I want to do this is that I'm looking for weighs to reduce the weight of my rather chubby Domane SL7 w/o sacrificing too much. I weigh ~165lbs and had 140mm discs on my last bike which was a Trek Boone. The smaller brakes gave me no issues for the riding I do (i.e., I never riding down any screaming mountain descents, etc.) 

I may start by doing a hybrid of just 140mm on the rear and see how that goes. If I go 140mm front and rear and it doesn't work out, I can always go back.


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## [email protected] (Jan 7, 2019)

You could run 140mm rotors on your bike once you remove the 160 adapters that are currently on the bike. The calipers would then direct mount to the frame and fork!


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## PoorInRichfield (Nov 30, 2013)

Thanks Mitch. Do you know _how_ the front caliper will attach to the fork once the spacer is removed? 

For the rear, it's obvious as the bolt heads that hold the caliper on are on the bottom of the chain stay. For the fork, however, if I remove the spacer that is bolted to the fork, I have no idea how I'd mount the caliper to the fork as the bolt holes for the spacer wouldn't be in the correct spot for the smaller rotor. What am I missing?


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## tlg (May 11, 2011)

PoorInRichfield said:


> Thanks Mitch. Do you know _how_ the front caliper will attach to the fork once the spacer is removed?
> 
> For the rear, it's obvious as the bolt heads that hold the caliper on are on the bottom of the chain stay. For the fork, however, if I remove the spacer that is bolted to the fork, I have no idea how I'd mount the caliper to the fork as the bolt holes for the spacer wouldn't be in the correct spot for the smaller rotor. What am I missing?


Flip the bracket. Doesn't it say "Up for 140" on the other side?

https://www.bike-discount.de/en/buy/shimano-140-160mm-front-flat-mount-adapter-732856


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## PoorInRichfield (Nov 30, 2013)

tlg said:


> Flip the bracket. Doesn't it say "Up for 140" on the other side?
> 
> https://www.bike-discount.de/en/buy/shimano-140-160mm-front-flat-mount-adapter-732856


LOL! Yes, it does, thanks! 

I thought the bracket just got removed, so it never occurred to me to look at what it said on the other side (which can only be read when the front wheel is removed).


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## jetdog9 (Jul 12, 2007)

Your weight savings there is what, 19-20 grams per rotor, 38-40 grams total, which amounts to about 0.084 pounds. You can say every bit matters, but that's not much.


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## [email protected] (Jan 7, 2019)

Glad someone mentioned the mount, slipped my mind that I didn't state you needed to flip the caliper mount (part number Y8N230000 for ref)


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## PoorInRichfield (Nov 30, 2013)

jetdog9 said:


> Your weight savings there is what, 19-20 grams per rotor, 38-40 grams total, which amounts to about 0.084 pounds. You can say every bit matters, but that's not much.


Yeah, I hear you. Short of saving a little here and a little there, I don't know of any way to start decreasing the weight of a nearly 20lbs bike short of buying a completely new bike. I know this bike isn't an Emonda, but I think there's a few places I can trim some weight that I won't notice. Hopefully the combination of all the weight savings I'm planning will add up to a pound or so.

With this brake modification, the plan is to go from Ultegra 160mm rotors to XTR 140mm rotors (which are lighter than Dura Ace rotors, supposedly). The stock seat on the bike is 300g and isn't fitting my keister so well, so I plan to get a new seat of which many are around 150g. I'm also looking at a light weight wheel set that still has 25mm internal width rims and ~35mm depth, but is several hundred grams less. 

I don't plan on doing this weight savings program overnight, but I figure if I trim a little at a time, maybe I can get my bike down to a weight that isn't so offensive 

Weight aside, the Domane SL7 is an amazing bike... it puts a smile on my face every time I ride it. However, every time I pick it up, I can't believe how much more it weighs than the 2014 Domane 5.2 that it replaced. (The two bikes can hardly be compared any more, but still...)


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## Coolhand (Jul 28, 2002)

Aoelus XXX 4 wheels.


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