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Discussion Starter · #1 ·
I have a 2019 stumpy that came with sram guide brakes (which I don't like). My mechanic has suggested replacing the stock rotors with a set of 2 piece rotors as they will shed heat better and will perform better, especially at high altitudes where this bike lives most of the year. The issue is the bike has 200/180 rotors, and the sram 2 piece rotors don't seem to come bigger than 180mm (which seems crazy to me). I looked at shimano, and their xtr rotors come in 203mm, not 200mm. Is there an issue using shimano rotors on an otherwise sram brake system, will the 3mm size difference cause problems, and does anyone else make a high end 2 piece rotor in 200/180?

Thanks
 

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Dirty Old Man
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There's always Hope.
Wheel Blue Spoke Bicycle wheel rim Transport


Personally, I had really good luck with the Shimano rotors, they were quiet and always straight. You may need to get the Shimano adapter for 203mm rotors, otherwise there's no issue. It's all pretty standardized.
 

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Discussion Starter · #3 ·
I am hoping that if I do this I can get shimano. I'll ask my bike mechanic, he's the one that suggested new rotors as a way to get better performance out of the substandard sram guide brakes on my stumpy. Thanks.
 

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Discussion Starter · #5 ·
Thanks, I understand that...but I'm trying not to spend $500-600 if possible. That's what xtr brakes would cost. It's an s works bike so I like to keep everything towards the high end to have a consistent build. I wish specialized had done the same.
 

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I have a 2019 stumpy that came with sram guide brakes (which I don't like). My mechanic has suggested replacing the stock rotors
If you don't like the brakes, you don't like the brakes. I wouldn't go throwing more money at something I don't like. Ask yourself if new rotors is going to make you like your Guides.

But to answer your question, if you change the rotor diameter, you'll need to do something about your adapter so the pads it the rotor at the right location.
 

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I did everything under the sun to get guides to an acceptable level of performance for me. In the end it was a waste of time and money. I'm on Saints for the past 2 seasons now and they are KILLER. Zee's are pretty cheap.
 

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I typed a response and lost it when searching for this article *bangs head*

https://enduro-mtb.com/en/best-mtb-disc-brake-can-buy/

Short answer, if a 200mm front rotor isn't powerful enough, you need more powerful brakes (that also modulate really well). e.g.
Hope
Magura MT5 / MT7
Code
Cura 2 or 4
Hayes
TRP

Also see:
https://www.vitalmtb.com/features/W...isc-Brakes-Reviewed-by-Vital-MTB-Members,2401
https://www.vitalmtb.com/features/Vital-MTB-Face-Off-The-Best-DH-Brakes,2152

...and I hate to be brandist, but ugly SRAM brakes don't have a place on an S-Works bike. It really deserves something like Hope's or Formula's.

Get rid of the brakes that are so ugly that they ought to be free, Roll with some style. Your bike deserves it. The first poster had it in one!
 

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My mechanic has suggested replacing the stock rotors with a set of 2 piece rotors as they will shed heat better and will perform better, especially at high altitudes where this bike lives most of the year.
Changing rotors has no bearing on brake performance. Unless size changes as well. If you want more brake then:

- get better pads
- get bigger rotors
- get bigger brakes

Is there an issue using shimano rotors on an otherwise sram brake system,
Yes. Shimano brakes use narrower brake track, so their rotors are not compatible with other brands. You can get away with it most of the time. However sometimes the arms of the spider that holds the brake surface on a shimano rotor can hit calipers of other brands.

will the 3mm size difference cause problems, and does anyone else make a high end 2 piece rotor in 200/180?
You will have to shim the caliper of the front brake by 1.5mm, or you will need a new adaptor appropriate for your fork.

Regarding the "better pads" - its a hairy issue. Usually "better" means sintered metallic, but there is no agreed upon standard what that means, so "sintered metallic" of one brand would be "semi metallic" of another. I use EBC gold pads.
 

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Yes. Shimano brakes use narrower brake track, so their rotors are not compatible with other brands. You can get away with it most of the time. However sometimes the arms of the spider that holds the brake surface on a shimano rotor can hit calipers of other brands.
I think I'm dealing with this right now actually with some magura trail sports. Pulsing brakes when using a narrow track rotor. Note: the magura rotors are also quite narrow due to their wavy shape.

Op, are you actually experiencing and heat related issues? If not I'd keep the same rotors are change the guides out.
 

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If you hate your Guides so much, sell them to me. I'll definitely dispose of them appropriately. I doubt changing rotors will make any difference, as numerous posters mention above. If you're already running big rotors and 4 piston brakes and it isn't enough, either you need to lose a lot of weight or it's a technique thing.
 

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Dirty Old Man
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If you hate your Guides so much, sell them to me. I'll definitely dispose of them appropriately. I doubt changing rotors will make any difference, as numerous posters mention above. If you're already running big rotors and 4 piston brakes and it isn't enough, either you need to lose a lot of weight or it's a technique thing.
I don't know about that. I've got Magura MT7s on my Trek and SRAM Guide REs (Guide lever w/Code 4 pot calipers) on my Specialized. Both running 203mm rotors. The difference in power between the Magura and SRAM brakes is vast. I previously had XT 4 pot brakes on the Trek and may put them on the Specialized as right now the SRAM brakes force me to readjust my braking markers on trails, forcing me to go slower and brake sooner. The Maguras will throw you over the bars.
 

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SRAM brakes force me to readjust my braking markers on trails, forcing me to go slower and brake sooner.
That is exactly my experience with sram brakes vs other 4 pot brakes.

I will say, if I lived in the 4 corners area etc., with lots of high consequence thread the needle type moves where breaking traction is paramount, sram brakes work great for that stuff.
 

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I don't know about that. I've got Magura MT7s on my Trek and SRAM Guide REs (Guide lever w/Code 4 pot calipers) on my Specialized. Both running 203mm rotors. The difference in power between the Magura and SRAM brakes is vast. I previously had XT 4 pot brakes on the Trek and may put them on the Specialized as right now the SRAM brakes force me to readjust my braking markers on trails, forcing me to go slower and brake sooner. The Maguras will throw you over the bars.
If your Guide REs won't lock up on every surface and eject you from the bike on demand, there's something wrong with them.
 

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Discussion Starter · #19 ·
So I did replace my sram rotors with xt. I don't understand why sram does not offer their two piece rotor in 200mm size but so be it. My mechanic did have to do minor adjustment to get them right. Anyway after a few rides on them I have to admit that the new rotors have improved breaking feel for me. No more oise and chattering that I was experiencing. I doubt if they are pulling harder but just having them quiet and smooth is enough improvement for me.

Sent from my SM-G950U1 using Tapatalk
 

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Good to hear you got it worked out. So if you are happy there is your proof. But I'd have said, like others, rotors won't solve your issues.

I've run XTs, Saints, and Guides. I've found the Guides to be the most reliable. I've had it with the wandering Shimano bite point and am weeding out Shimano brakes.

The wander Shimi bite point is particularly bad in cold weather and I do a lot of that, and its on very slick rocky turf.

Not sure where the hate for the Guides is coming from. I can lock up the front and rear wheel without issue (so, that braking power table doesn't mean much to me). I can feather the brake. No wandering bite point. Need bled less often than the Shimi's. What's not to like?

My Saints have a new set of Codes waiting to replace them.
 
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