The Triumph Dolomite Club - Discussion Forum

xvivalve wrote: Whilst it is only a difference of 4 mm, it represents a reduction in XSA to 62%, so the travel of the wheel cylinder piston will be increased by a proportional amount thereby reducing pedal travel before the shoes lock with the drum.

Up to WF68200 used GWC1502 (same as 1300 and 1500), after that VIN the 1850 used GWC1121 (same as Sprint)

Correct but there are smaller ones. I don't have the data by hand but the Triumph shape wheel cylinders are fitted on more cars, I believe some Fords. The Triumphs are about 17 and 19mm and there is a 15mm version also. So not a Triumph part but it is a direct fit.

Jeroen

Why does everyone insist on describing these things in metric when they were built Imperial?

Sprint cylinders are 3/4" bore, 1300, 1500 and early 1850 are 5/8" bore (16 mm near as makes no difference) I believe a 11/16" cylinder was offered for something (1500FWD maybe?) at one point, these seem to be NLA but why bother anyway?

When doing a TJ convo, especially with a dual M/cyl, I specify 1500 rear cylinders when buying, as these seem to stay constant at 5/8" throughout.

Steve

My understanding is that when the Sprint dual circuit brakes were introduced, the rear wheel cylinder size was dropped to 5/8" diameter so that if total loss of fluid occurred on the front brake circuit, there was sufficient fluid remaining in the rear brake system to operate the rear brakes (which there possibly would not be with the standard 11/16" diameter bores). That applies to the standard fitment dual circuit master cylinder and will be influenced by how well the rear brake shoes are adjusted and how well the adjusters are working (ie how much fluid is used just to bring the shoes into contact with the drums)

I believe that is why suppliers (eg Rimmers) now only offer the 5/8" cylinders for the Sprint. I hope there are no conversions being undertaken without the rear wheel cylinder size being checked and changed if necessary. Worth checking this if a master cylinder replacement for another type/size is made.

Geoff

gmsclassics wrote: ↑Sun Mar 27, 2022 10:09 pm My understanding is that when the Sprint dual circuit brakes were introduced, the rear wheel cylinder size was dropped to 5/8" diameter so that if total loss of fluid occurred on the front brake circuit, there was sufficient fluid remaining in the rear brake system to operate the rear brakes (which there possibly would not be with the standard 11/16" diameter bores). That applies to the standard fitment dual circuit master cylinder and will be influenced by how well the rear brake shoes are adjusted and how well the adjusters are working (ie how much fluid is used just to bring the shoes into contact with the drums)

I believe that is why suppliers (eg Rimmers) now only offer the 5/8" cylinders for the Sprint. I hope there are no conversions being undertaken without the rear wheel cylinder size being checked and changed if necessary. Worth checking this if a master cylinder replacement for another type/size is made.

Geoff

Parts list (and my memory) says no to the 5/8" cylinder on any Sprint, even dual circuit. Wishful thinking/urban myth i'm afraid.

If Rimmers are now only selling the 5/8" cylinder as 1 size fits all, that's pretty poor practise, pure laziness! And one more reason why I only use Rimmers as SoLR (Supplier of Last Resort) Fitchetts know the difference and have at least 3/4" and 5/8" in stock.

I'm quite surprised the factory DIDN'T do something like fit a smaller bore rear cylinder to go with the Tandem master after all the tandem master is 2 master cylinders in tandem, so 2 lots of free play. I've never had a discernible long pedal on single circuit TJ fitted car, but it's pretty endemic on the tandem master cars. (Including both of mine), fitting the 5/8" cylinders and ditching the LSV really helps with that, i've never seriously considered upping the M/cyl bore, no need! What IS evident with regular use, though, is you DO need to keep the rear adjustment setup correctly or you'll find the pedal going away from you, I reckon with my daily drivers to set the shoes up at least every 6 months (or when the handbrake stops working, whichever comes first!)

Steve

Carledo wrote: ↑Sun Mar 27, 2022 2:01 pm Why does everyone insist on describing these things in metric when they were built Imperial?

Steve

I alway's use a tape measurer and then it's near 17mm.

Jeroen

soe8m wrote: ↑Mon Mar 28, 2022 10:14 pm

Carledo wrote: ↑Sun Mar 27, 2022 2:01 pm Why does everyone insist on describing these things in metric when they were built Imperial?

Steve

I alway's use a tape measurer and then it's near 17mm.

Jeroen

Here in Britain we have tape measures that measure in metric on one side and imperial on the other. I can send you one if you can't them there in Europe!

Steve

Carledo wrote:
Here in Britain we have tape measures that measure in metric on one side and imperial on the other. I can send you one if you can't them there in Europe!

Steve

Ah, you are improving things already I see.

Jeroen

Carledo wrote: ↑Sun Mar 27, 2022 2:01 pm Why does everyone insist on describing these things in metric when they were built Imperial?

Steve

For similar reasons that a 5p piece is no longer referred to as a ‘shilling’, maybe…

Bummer…just removed and measure my rear brake cylinders and they’re 19mm 3/4 inch !! For a TJ car, 16mm 5/8 are recommended, right ?

Like these…

https://www.ebay.co.uk/itm/292237101764 ... media=COPY

Thanks, Richard

RichardHyde wrote: ↑Sat Apr 01, 2023 1:12 pm Bummer…just removed and measure my rear brake cylinders and they’re 19mm 3/4 inch !! For a TJ car, 16mm 5/8 are recommended, right ?

Like these…

https://www.ebay.co.uk/itm/292237101764 ... media=COPY

Thanks, Richard

Correct, though these are incorrectly labelled as standard Sprint (and GT6 which IS correct)

RichardHyde wrote: ↑Sat Apr 01, 2023 1:12 pm Bummer…just removed and measure my rear brake cylinders and they’re 19mm 3/4 inch !! For a TJ car, 16mm 5/8 are recommended, right ?

Like these…

https://www.ebay.co.uk/itm/292237101764 ... media=COPY

Thanks, Richard

Richard,

Do you want me to look out those new wheel cylinders I mentioned to you a while back?

Glen.

Im relatively new to this site, but have a long history of building modified cars,
My personal preference would be run a longer pedal travel that should give you more feel to the brakes, again, I like to run NO servo, the servo will reduce the feedback from the brakes, you can buy adjustable proportioning valves for brakes, these allow you to dial in the rear retardation so you get the front brakes to lock before the rear ones, and preferably dont lock at all, as this will only encourage the rear of the car to come round.
and the most important piece of the braking system is the bit people often forget, The TIRES, if you are running hard old tyres you can compromise all the time and effort you have put into getting the brakes better, do the research, what tire has the best braking capabilities... does it matter if they only will last 15k, I would imagine the average mileage of our triumphs is below 3k a year, the tires have worn out in 5 years, which is fine by me,
I doubt if I am the only one have run TOYO888r (soft compound) street legal semi slicks on the road on this site, The change in braking dynamics is massive.... the downside is the life of them is abysmal.

Interestingly, I have a pair of NOS Unipart cylinders with boxes correctly marked up for the Sprint (and late 1850) as GWC1121 and the castings inside are embossed 5/8"

I also have a Girling NOS boxed cylinder seal kit for the Sprint and the uncompressed seals measure as 0.634" which is just over 5/8"....