Hitchcocks Forum

Hello to all! I have just bought a '98 350 Bullet Indian Export Chrome model.
My plan is to modify it into a trials type bike and need to get some trials type tyres.

My question is will a 4.00 - 19 tyre fit into the swinging arm? has anybody fitted one or do i keep trying to find a 3.50 - 19 tyre which seems a lot harder to come by?

I think it's a firm "maybe". I'm reasonably convinced I wouldn't get one in my 350 bullet looking at how close the 3.50 x 19 comes but others claim to have squeezed one in there.

Heidnau K67 comes in 3.50x19

It does occurr to me that the size of the contact patch on a 3.50x19 is probably about the same size, maybe even bigger than the 4.00 x 18 they put on most classic trials bikes. I have a similar thing with the 29" tyres on my mountain bike, they look desperately skinny compared to the 26" standard ones but I actually have more rubber on the ground.

The other option is to fit a swinging arm capable of taking a wheel with a wider tyre.

The good news is that our hosts sell one, part no. 92602 in the accessory catalogue.

The bad news is that it costs over £300 with VAT!

A.

Hi, early redditch trials bullets were fitted with 4x19 tyres and didnt have widened swingarm. This was the standard size trials tyre of the period. Vince

The Heidenau tyre has its outer row of “knobbles” at an angle so the tyre is perhaps wider overall than the equivalent size old “trials universal” types.

Having used a 3.25 on rear of my bike (it was too wide for the front mudguard so I used it on the back wheel rather than try to send it back), I think a 3.50 would be the best option because a 4.00 might catch somewhere.

Thanks for your replies - I have now removed the rear wheel and there is no way that the 4.00 - 19 is going to go in there. I have managed to source an Ensign 3.50 - 19 from the Classic Tyre Store so I will post on here if it fits....

The Ensign 3.50 x 19 will fit fine.

stinkwheel wrote: ↑

Thu Apr 01, 2021 10:36 pm

It does occurr to me that the size of the contact patch on a 3.50x19 is probably about the same size, maybe even bigger than the 4.00 x 18 they put on most classic trials bikes

I have a bike with 3.50x19 and one with 4.00x19. To look at you'd be hard pressed to tell the difference, try going up a muddy slope or giving it a handful while turning and you know which is the 4.00 though.

To make the 4.00 fit properly you need grind down the most forward mount for the chain guard, partially.

Sure, but don't most classic trials bikes have a 4.00 x 18 rear? Which is what I was alluding to when comparing contact patch sizes.. Goes without saying that a 4.00 x 19 is going to have more grip than a 3.50x19.

Hi, 4.00x 19 was the standard size for classic trials. 4.00 x 18 became the norm because the 19 tyres were no longer available. I have to fit an 18 rim and tyre to my AJS for that reason. Incidentally the chainguard forward mount is different on early bullets. Vince.