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Complete newbie here, looking for better stopping power and less rusty calipers.

I have a Nishiki Custom Sport with Dia Compe brakes and I was wondering if I could use the Shimano 105 5800's on them.

I've heard conflicting comments on the compatibility with the SLR design and the pull ratio (they state you need "ST-5800, ST-6800 or ST-9000 STIs for correct leverage ratio").

I kind of understand it, kind of don't.

My biggest concern is safety so that's what I'm trying to gauge at (that and the recessed mounting).

Thanks!

  • Commenting because not an answer. Depends if you're trying to maintain originality look or not. Personally I want to be safe on my bike, so the mid 90s alu road bike got modern tiagra dual pivots, which work fine for me. Do keep your old brake parts stored for any future rebuild. Consider wheel size - 27" are ~4mm bigger than 700c wheel rims so bear in mind brake pad offsets.. As for brake pull, I don't have an answer. – Criggie Aug 26 '16 at 22:06
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    I'm all about having functionality over aesthetics, but that's a good idea for storing the parts. Thanks. – Robert Lee Aug 26 '16 at 23:02
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For many years, all brake levers had a cable pull for either traditional sidepull/canti/u-brake brakes or linear pull/mechanical disc brakes. There were small differences between levers but essentially every lever across all bike genres in one camp would work with every brake in that camp. When Shimano came out with their under-tape shift housing routing STIs, they changed their brake lever pull to a higher number, putting it pretty much in between the two existing classes. These levers and brakes are designated Super SLR and they include most of the current Shimano brakes.

It's more cable pull. What that means is if you pair Super SLR levers with conventional sidepull brakes, you'll have more rapid arm movement and nice crisp brake feel but less leverage and less power. If you pair Super SLR brakes with conventional levers you'll have the opposite: more leverage but mushy feel and less arm movement, forcing you to have the starting position of the pads very close to the rim if you're going to avoid running out of lever travel.

I don't really recommend doing either. The danger of the former is inadequate braking power, and of the latter it's that it can be easy to run out of lever travel, which is also a safety issue, plus the lever feel is poor.

  • Thanks for the insight. I've only seen this issue with the SLR design - would I need to worry about any other compatibility issues (like cable pull instead of the normal reach, mounting, etc.) with other brands? Obviously not from older Shimanos, but I was also looking at the Tektro R539 and wasn't sure if I wanted to quite drop ~$130+ for new Shimano levers. – Robert Lee Aug 26 '16 at 23:04
  • It's "Super SLR" that this applies to. Regular "SLR" is Shimano's old name for all their brakes/levers (SLR was their name for the fairly legitimate innovation of having a return spring in both the lever and the brake). You do have some other compatibility concerns. You need to make sure the brake arm reach is correct for the frame/fork you've got, and if your frame/fork don't take recessed brake mounting nuts then you'll need to get brakes that either don't have them (the studs will be much longer) or employ a hack approach to make brakes intended for recessed nut mounting work. – Nathan Knutson Aug 27 '16 at 0:46
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A couple years back I put a pair of 105 5800's on a 1986 Centurion Elite RS that had Diacompe brake levers. It worked great. I never even considered that the pull ratio would be an issue perhaps I should have? I have heard of pull ratio being an issue when trying to use cantilever brakes, linear pull (v-braves), or disk brakes with vintage road brake levers, but in my case... my 5800s worked with my 1986 diacompe levers just fine.

  • Yeah most of it was with regard to anything other than single/dual pivot brakes, but I still saw conflicting information that was hard to tell if it was just nitpicking or actual issues. – Robert Lee Aug 26 '16 at 22:21
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maybe.. but probably not. Older bikes usually require the calipers to have more reach. 105 or similar have up to 49mm of reach whereas with an older bike you may need up to 57 mm . Shimano make them as do Dia Compe. A good bikeshop should be able to get them otherwise buy online easy enough.enter image description here

Here is a picture of an older bike I rebuilt with new Shimano calipers. Tiagra or 105 would not work as the drop reach was not sufficient. The pads would graze the tyres even in their lowest position. These ones with 57 mm reach are fine and work well with an older set of Shimano 8 speed STI levers..

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    Edited to use the proper terminology - reach, not drop. – RoboKaren Oct 6 '16 at 4:26

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