Brake disc offset question, does 0.5mm make a difference between 1992 and 1993 GSXR11

[IronPawz]

My modified Katana is finally getting some loving and it needs front discs. First thing I find is I am not sure if the front end is off a 92 or 93 GSXR1100. The difference is 0.5mm for the offset (my guide taken from here https://www.isrbrakes.se/products/brakediscs/standard/)

Model Year ISR Part.No Disc diameter Central Whole Diameter' Bolt pitch diameter Bolt hole size Swept height Offset

GSXR 1100 85-92 23A-SU310-03 310 64 86 10 36 22
GSXR 1100 93- 23A-SU310-04 310 64 86 10 36 22.5

It is not that easy to determine 0.5mm trying to measure a caliper. Perhaps it doesn't matter in which case why did they change it? The forks other than this as I understand it are the same. I see people advertising discs that are suppose to support everything from about 89 - 97. I quite like these ones https://www.sbs.dk/products-1/brake-discs/5270 however they don't provide an offset (shop is checking).

I seen things where people say this 'should' be fine given the floating bits and calipers self aligning etc. Others not at the thickness of the discs also varies this can increase the offset. Then there are spacers if it needs to be further out so perhaps get the smaller offset and shim it if needed? I wondered it the "fits all" ones are in between or it is considered 0.5 makes no difference.

The calipers are six pot nissin. I'd really like to set it up with radials sometime too (really just because they suit that old style modernised look).

There are some old images of this bike here:
https://www.kiwibiker.co.nz/forums/showthread.php/180722-Suzuki-Katana-1100sz/page9?highlight=ironpawz

[IronPawz]

Here is one claiming to do them all
https://motorcyclepartswarehouse.co.uk/rezo-wavy-stainless-front-brake-disc-pair-suzuki-gsx-r-750-gsx-r-1100-89-96.html

And another clearly for 93 onwards (1100)
https://www.ebay.com/itm/Front-Rear-Brake-Discs-Rotors-Pads-GSXR1100-93-98-97-96-GSXR750-94-95-For-Suzuki-/254780624088

One for pre 93 only (1100)
https://www.ebay.com/itm/Front-Brake-Rotor-Pads-for-Suzuki-GSXR-600-92-93-GSXR-750-88-93-1100-89-92/222403368844?fits=Year%3A1992%7CModel%3AGSXR1100&hash=item33c846178c:g:Ut8AAOSwopRYm4FE

Also on the bike now are a different set of discs that never worked properly. I was told they are dished so the caliper has to take up the process of straightening them before clamping (and I've never been able to get the leaver to not come to the bar with these ones but I did recon the calipers myself same time). I wondered if they have the wrong offset and therefore that is the issue. Clearly I've little idea about these things...

[IronPawz]

I just found the original forum for the old Kat's build which is quite detailed.

https://www.thegsresources.com/_forum/showthread.php?80503-Building-a-KiwiKat&highlight=katanakid

It clearly states on page two these legs are "The legs and triples are GSXR1100 WP/R/S" which means they should have the 22.5mm offset verses 22.0 case closed on what it is.
Case open on if it matters? Some sellers do not seem to think so but perhaps they built 22.25mm offset (I kind of doubt it but I would not rule it out they seem to all be nock offs).

[malcy25]

Given your pad wear for each pad is probably 3mm or more, I personally wouldn't care.

I would check to make sure the disc is relatively central in the caliper though, But 0.5mm I doubt you'd see and any bike that has had alternative combos of discs and calipers are probably not that close.

[IronPawz]

Cool and thanks. Good point on all those modifieds out there. I was thinking if its a big issue I'd see people discussing it more but it pays to see what experienced people think.

For now I'm just interested in having it all work (given it has a WOF and Rego I'm keen to ride it more). If it still has issues I'll look at different calipers and master. I know the 6 pots are notorious to bleed and I see plenty about their standard master being not great for them. I'd start with the master and if its still not right go for the calipers. Lighter 4 pots or if I can radial conversion.


Given your pad wear for each pad is probably 3mm or more, I personally wouldn't care.

I would check to make sure the disc is relatively central in the caliper though, But 0.5mm I doubt you'd see and any bike that has had alternative combos of discs and calipers are probably not that close.

[Kickaha]

I know the 6 pots are notorious to bleed and I see plenty about their standard master being not great for them.

Standard m/c is probably too small for the 6 pot, master cylinder sizes need to be matched to he calipers you use

[pete376403]

Standard m/c is probably too small for the 6 pot, master cylinder sizes need to be matched to he calipers you use

A smaller master cylinder would give more braking force at the expense of greater lever travel, that is as long as the smaller master cylinder would move enough brake fluid to move the pads into contact with the disks.

[malcy25]

On old school non radial master cylinders it’s all about area of master cyl relative to total piston area. I recall my brother doing a lot of work on this and. Circa 27:1 is a good number.

This is not his work, but confirmed it http://kawatriple.com/tips/mastercyl/mastrcylratio.htm

[pete376403]

On old school non radial master cylinders it’s all about area of master cyl relative to total piston area. I recall my brother doing a lot of work on this and. Circa 27:1 is a good number.

This is not his work, but confirmed it http://kawatriple.com/tips/mastercyl/mastrcylratio.htm

Its basic hydraulics. The orientation of the mounting bolts shouldn't (can't) make any difference.

[F5 Dave]

He means radial mc not calliper which i think you have misread. Radial mc is about leverage change included into the hydraulic advantage, which is just leverage by another vector.

Sorry did we skip by the point that you will need an lvv certificate for any braking component change not like for like?

Also 6 pots are usually panned for encouraging drag and hence warping discs. Maybe not so much a problem on little used bike.

I would totally prefer a swap to RF900/GSXR 750 1100 90s Nissin 4 pots. Avoid Tokico ideally.

[pete376403]

radial vs axial mount, the hydraulics are still the same.

[ellipsis]

...and at the end of the day most fuks don't know how to brake, ditch or try another option to avoid the consequence of speed, mass and kinetic indifference to humans on g-machines...


..Life 101...anything can happen in the next half hour...

[F5 Dave]

radial vs axial mount, the hydraulics are still the same.
Of course they are but there is a conversion as a 19mm will be the equivalent of a 5/8 or thereabouts because the fulcrum is in a different place. More mechanical advantage overcomes less hydraulic advantage. But the supposed 'advantage ' is a direct push rather than a rubbing one.