Thumb Brakes legal for Vintage?

I've spent some time searching this on the forum, particularly looking for posts in reference to vintage classes.

Due to the exhaust system on my bike and the consequential design I had to settle with for my rear-sets, I found I had no room for a brake pedal that would be effective yet not be fouled by the kicker.

(yeah, I know I could just toss the kicker)

So I'm in the final stages of of fabbing up a thumb brake rig for the bike and I'm curious if there is any reason it would be determined illegal. The rulebook states that the operating principle must have been around for the era of the class. One could posit that hand-operated hydraulic brakes were indeed around for V4 machines, yet the first I'd ever heard of a thumb brake was Doohan's after his ankle-debilitating crash ~early nineties.

Any opinions, or ideally, a pronouncement from Mongo?

Thanks!

 

Understood. I wasn't planning on using this as a race bike when I modified it 18 years ago, so the exhaust wasn't a big concern because at that time I was just staying with the stock foot gear.
A happy accident was that the exhaust works pretty well and I'm apprehensive to change it.
I am fairly confident it won't be a problem for track days and I'm eager to get it on the track, so that is why I just resigned myself to the thumb rig. If it doesn't fit with the intention/spirit of vintage, then I suppose I can make the time to get something figured out...or just toss the kicker if the bike is going to be enthusiastic about bump starting. I haven't ridden it at all since I dug it out of the barn, but it kicks to life just fine.
I'll wait for your decision.

 

Brakes? We don’t need no stinking brakes! That being said, while it may not apply within the “spirit” of the rules, it’s hard to see how a rear thumb brake could be considered a performance advantage.

 

Since I am considering putting a thumb brake on the RGV, I am interested in this as well, but since it will run in a basically unlimited GP class, I am not sure that the rule applies to my situation. Still, I would like to know the legalities of it.

I only ever really used the rear brake in the rain and for helping control wheelies, but I think that a thumb brake would have better feel than the foot brake, allowing for finer inputs.

 

IMO unless you have a physical disability where you can't use your right foot to brake, it should not be legal in Vintage below the V6 classes. Legal in V6 and up classes seems legit to me.

 

This ^^^^


(Not that my opinion really matters...)

 

Yeah, I think I recall thumb brakes being period pieces about circa 1930 . . . .

All the IOM racers had 'em in the '50's & 60's. Look at Surtees' and Ago's and Hailwood's stuff . . . thumb brakes on 'em all.

No doubt that's a Vintage item.

I had issues with my exhaust on my PPIHC twins . . . . I changed the rearsets and exhaust and bent the kicker. Geez, all I had to do was build it the most convenient way and use a modern thumb brake. How stupid was that of me?

Cheers,

dave

 

I would vote for no on a V4 bike.

 

What bike and what class?

 

I would have no problem with it..

 

Disc brakes on GP bikes then, they were around in the period unlike thumb brakes.

 

It's for a 1981 XS650 I'm considering running in V4.

FWIW, all of the arguments for and against are reasonable; I've gone through many of them in my own mind.

In regard to the disability argument, I'd leave the rear brake on my 87 GSXR a little soft because I had a hard time hanging off without activating it due to an oooold snowmobile injury to my ankle.
However, I certainly can't claim that I'm disabled. The info in my original post pretty much lays out the premise that it's more about a convenient and expeditious method of fitting a rear brake master cylinder...and I thought it might be kinda cool. I really only consider the rear brake an emergency brake or for convenience to hold the bike still.

 

I thought kick starters were not allowed to remain on a bike for racing. ?
If it's a case of interference between the starter and brake lever, would a folding toe piece on the brake lever alleviate that clearance problem?

 

I assume you are pulling off the kick lever after the bike cranks up? Couldn't you use a torch to bend the kick start lever to fit around the brake lever for the few seconds you need to have it on the bike?

 

I know that Yamaha likes to use economy of scale, so if you have a straight kicker, could you fit an RZ350 kicker, which has a bend at the bottom, that allows it to go around foot pegs? I know that using the RZ kicker is a common upgrade for RD350/400 folks with fixed rearsets instead of the ground-fouling footpeg brackets.

 

Wow, I appreciate all the suggestions, and yes, the expedient solution to the kicker issue is to toss it after start-up...unless (paraphrasing rulebook) "it can be secured in the stowed position". I would, however like to be able to do some canyon riding and track days too.

I've already heated and bent the kicker to avoid fouling the pipe and foot peg, but things are pretty tight and the pedal would end up right around the clampy pivot piece that won't tolerate any modification. A folding peg may work, but if it is configured so that it "falls" into place, or is spring loaded to do such, it would be a major PITA.

If my phone wasn't an outdated POS I would upload a photo or two and it would likely be made very clear what sort of pickle I'm in.

yeah, Yamaha sure does like to do their "parts-bin-bikes". I haven't explored alternative kickers, but like I said above, the shaft and clampy part are going to be hard to get around (figuratively and literally!)

I guess I ought to say I'm more or less committed to the thumb rig; I was mostly looking for a ruling as I thought it might be fun to compete again. If it's not something appropriate, I'm not going to be bothered; I'll stick to the track days and perhaps break out my 87 GSXR if the competition bug bites hard enough. I just don't care about the XS as much as my GSXR, so I figured I'd rather beat up the XS .

 

I'm following, and wondering if a thumb brake gives a rider any advantage over a foot brake on a vintage bike?