First post - compatible caliper upgrades with Sora 3500 STIs

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First post - compatible caliper upgrades with Sora 3500 STIs

Postby CallumCycles » 10 Aug 2019, 1:09am


I currently have a 2015 cube peleton pro running on the ever aging Sora 3500 GS. I'd like to upgrade bits and bobs slowly starting with the calipers. I'm looking at ultegra 6800 calipers but have a question about compatibility, I've read in some places that these would be incompatible with 3500 STIs because of different lever pull ratios but from my interpretation of the Shimano compatibility chart they are compatible? Am I reading the chart wrong that the entire upper left box of STIs is compatible with the entire upper right box of calipers? Has anyone tried such a ludicrous upgrade 3500 to 6800 calipers.? Would I be safer upgrading to 105 5700 calipers? There's only a few quid in it on eBay so I'd like to get the best value for money whilst maintaining compatibility.

Cheers in advance

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Re: First post - compatible caliper upgrades with Sora 3500 STIs

Postby Spinners » 10 Aug 2019, 6:35am

I had a couple of bikes using Sora 3500 (one double and one triple) and the Sora brakes were the only disappointment. Everything else was superb and the triple will see action again sometime in the future.

Yes, I read the Shimano brake compatibilty chart the same as you but I also understand that there has been a change in 'pull' so I'd look for same generation brakes (i.e. where the STI's had sticky out gear cables) but in a higher groupset.
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Re: First post - compatible caliper upgrades with Sora 3500 STIs

Postby Brucey » 10 Aug 2019, 8:27am

the issue here is that most (only a couple of exceptions) new STI models launched after 2008 use what shimano initially called 'New Super SLR' (NSSLR) cable pull. You may see later references to 'SLR' but this is sloppy marketing; shimano already called a load of levers 'SLR' about thirty years ago and these are not anything like the same as current NSSLR levers.

Anyway ST-3500 are NSSLR type, so you can use it with any of the calipers as indicated in the chart (the different colours on the chart indicate current vs recent models I think). There are fancy linkages which appear in some brakes (which may increase the MA yet further) but otherwise cheaper calipers differ fundamentally from the more expensive shimano ones in only two main respects

1) brake blocks
2) centre bearing construction

shows the simplified bearing construction vs posher brakes such as BR-5700 (see item #6)

My gut feeling is that the brake blocks make more difference than the centre bearing. The other thing is that the brake performance varies enormously with the brake reach. In theory (with current NSSLR brakes, this did not apply many years ago, and doesn't apply to BR-R650 etc) the brake mechanical advantage (MA) is the same for different models of brake when the brake blocks are set to the middle of the slot, but varies (depending on the frame the brake is fitted to) whenever the brake blocks are in the top pf the slot (high MA = more power) vs the bottom of the slot (low MA = lower power).

This means that if you have the choice of two different reach brakes, and one is only just long enough (i.e. you will have to set the brake blocks at the bottom of the slot) you may get less brake power than with a longer reach brake where the brake blocks are set at the top of the slots.

Brakes can (and almost invariably do, using factory fitted cables not in the first flush of youth) also feel rubbish because of the cables.

So in general terms I'd suggest attention to lubing the brake caliper pivots, to brake blocks and to cables might make your brakes work better. If you buy new calipers you might still be left with rubbish brakes if the cables are bad.


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Re: First post - compatible caliper upgrades with Sora 3500 STIs

Postby tincaman » 13 Aug 2019, 3:09pm

I have Sora 3500 shifters combined with 105 5800 brakeset with Ultegra pads, all works well