GT750J front end on a T500

[Fritz500]

Hi,
Some time ago I purchased parts for a 72 GT750 front end (triple clamps, forks and drum brake) from various sources to mount on my 72 T500. I fitted the triple clamps and was trying to mount the front wheel when I noticed the axle was about 10mm too short. The axle came with the front wheel so I assumed it was the original one.

Can someone measure their axle and tell me if I have the right one?

My front axle measures 236mm (about 9 5/16") overall.

I have a couple of sets of GT750J triple clamps that have the same fork spacing so I assume the axle is wrong.

Anyone able to advise?

Cheers

Geoff

[jabcb]

The GT550J & GT750J have the same front brake but the axle part numbers are different.

Are the front wheel + axle from a GT550J?
If so, looks like you'll need to get a GT750J axle + associated parts.

I also have a 4LS front wheel + forks.
Have been thinking about putting them on my 75 T500.
Would be interesting to see the issues you run into & how it works out.

[Alan H]

A friend put the entire GT750 front end on his T500.
Not using the original T500 triple tree.

[Fritz500]

The GT550J & GT750J have the same front brake but the axle part numbers are different.

Are the front wheel + axle from a GT550J?
If so, looks like you'll need to get a GT750J axle + associated parts.

I also have a 4LS front wheel + forks.
Have been thinking about putting them on my 75 T500.
Would be interesting to see the issues you run into & how it works out.

The front brake + axle were bought off eBay about two years ago and were advertised as coming from a GT750. I put GT750 triple clamps on the T500 but the fork tubes are spaced about 5mm too wide so I need to put a 2.5mm washer each side of the brake. Then when I fed the axle through it was about 10mm too short.

Something doesn't add up.

The axle I have sure looks like a GT750J one but it obviously isn't. I contacted a seller on eBay who has one for sale and asked him to measure it. It is the same length (236mm) as mine.

Not sure what is going on...

Regards

Geoff

[tz375]

The GT550 front drum and axle I have has a 239mm OAL axle. The disk brake front axles I have are 245mm OAL (+/- 1mm).

I replaced the drum with a pair of forks and front wheel off a GT750 (don't remember the year) and kept the 550 triples and that all mounted up easily. I don't recall the 750 axle looking too long in the 550 but now you have me wondering

And if the brakes are the same on a 550 and 750 and the sliders are the same but triples are different, how is the extra width on a 750 taken up? Are the spacers longer or do they just pull further into the end caps.

The drum axle I have is plain at the end where a disk 750 has a round end that will not pull through the end cap and is presumably there to locate the disk relative to the caliper. Maybe that's the answer. The end spacers simply pull further in on a 750. If that's the case, it should be possible to use a 750 axle and perhaps the stock spacers but may need some new ones machined (or washers) .

[Fritz500]

tz375,

So I have to buy a disc braked axle...mmm. The length seems right. I'll ask a few eBay folks who are selling axles for disc brake GT550/750s to measure the lengths.

Regards

Geoff

[tz375]

OK, just to add to the confusion. This was bugging me so I double checked the two axles and that revealed nothing new. So I took the pair of GT550J fork legs - not 750J so that may be the difference.

Inserted two legs into a pair of GT750 triple clamps and turned them upside down and removed the bottom caps for the big reveal.

Then I took the GT550J drum brake assembly and its (short) axle and nut and it was a tight but perfect fit in the fork sliders. No side play at all and no shortage or excess of axle length.

Obviously the offset at the axle clamp is different so I grabbed a pair of GT750K, sliders (disk and drum provisions) and a set of GT750L legs and a set of GT750B sliders and the offset is the same as the GT550 sliders, so that isn't it.

So now I am officially confused. ON my GT750 triples a GT550 drum fits like it was meant to be there. Your axle sounds like it's only 3mm shorter so I see no reason why it won't all slide together for you. There is something different on your set up and it is possibly the 750J sliders but I doubt that.

Is there any way you could post pictures of that 10mm shortness? Is the drum a loose fit or tight fit between the legs?

If you need a disk front axle, I have a spare one for the price of postage but I should check it works first.

[Fritz500]

tz375,
Thanks for your experimenting!

When the drum is in place there is a total of 5mm free play side to side. Other measurements confirm a 2.5mm washer on either side centralises the drum between the forks.

Photos as requested...hope they make sense.


The gap between the inside of the fork sliders at the axle holders is 167mm.



The far side end of the axle is hard up against the axle holder...



You can see the end of the axle inside the nut...way too short.



I don't think the triple trees are GT750J ones despite what the eBay seller sold me. I can get the axle machined or buy anther one to suit.

If you have a longer axle and don't require it I like to purchase it if that will fix this curious issue.


Geoff

[jabcb]

Did some Google searches on this a while back.

The answer my exist in other forums where members discuss adapting the Suzuki 4LS front brake to other bikes.
They claim that the total width (hub + brake panels) is wider for the GT750 than the GT550.
Some of their members seem to claim experience using both & talk of machining the GT750 brake panels to reduce width.

But the online Suzuki parts diagrams do not support this.
Maybe they are right & the parts diagrams are in error.
Maybe the GT750 & GT550 brake panels actually are different.

[Fritz500]

jabcb,
No no no no don't add to my confusion!

I bought the front brake almost 90% complete off eBay a few years ago when planning this project. Once I got it delivered I realised the seller had put it together from numerous sources. The central hub was NOS and was in mint condition. The LHS and RHS brakes looked a bit worse for wear and took a lot of sanding and polishing to clean up. Not all the linkages were there so I ended up buying another LHS brade that came with all the links I needed.

The brakes came with the top triple clamp - I found a lower triple clamp that also came another top clamp. I now have a complete front brake that looks great polished and assembled. I now have a few spares that I'll put up on eBay or swap for other stuff I need.

The forks and sliders came from eBay - the fork tubes were rough but the sliders were quite good. I found some NOS tubes and they all fitted together quite nicely. I hope they work better than the original T500 forks (anything would be better!)

I'm sort of not surprised some things aren't fitting as Murphy (of Murphy's Law fame) doesn't sleep...

Thanks to those folks who have responded so far.

Cheers


Geoff

[tz375]

That axle is different to my GT550 axle but the distances are all different. How far is it between the fork legs (Triple clamp ctr to ctr distance)?

With the 550 axle in 550 sliders in 750 triples


nut end


other end


With a GT750 disk brake axle in the same set up.


GT550 and GT750 axles spooning when they thought no one was looking


I ran out to the shop and it looks like 154mm (+/- a mm or 2) between the posts and that's a long way from your measurement. It appears that the fork triples are different to mine, so I'll compare them to a different set later and see what that reveals if anything.

[Fritz500]

tz375,

Those two axles spooning is pure two stroke porn...

I'll go looking around the Internet for other attempts at this conversion but it's pretty clear from your photos what I have to do.

Cheers

Geoff