Tire size

[taz]

Noticed both tires are badly cracked on my 72 Wombat , What is the widest on front and rear I can go ?? Thanks

[olddogs]

Knobby or Universal tread, the style that came stock on the bike?

Finding the right size rear knobby can be a challenge, and using too large a tire just leads to sprocket and chain wear as well as increased load on the engine. Do a search. Much discussion on this topic has passed through this site.

[taz]

Knobby or Universal tread, the style that came stock on the bike?

Finding the right size rear knobby can be a challenge, and using too large a tire just leads to sprocket and chain wear as well as increased load on the engine. Do a search. Much discussion on this topic has passed through this site.

Just looking for the stock type with maybe 0ne or two size fatter .. Thanks ....

[Zyx]

Very few manufacturers these days make tires in the sizes used in the 70's. Stock tires were 2.75 x 21 Nitto Trials, rear were 3.50 x 18 Nitto Trials. Some trials tires are still offered in those sizes. Motocross tires are nearly all metric these days. Width of tires varies between brands and styles so there is no consistent answer in metric tires. I am using 80/100 x 21 front and 100/100 x 18 rear in a Kenda motocross style on what was originally a 100B, and fitting the rear tire was not easy. It is the equivalent of a 4.50 x 18 where a 3.50 trials tire was intended. The front was not an issue. You may be able to use these sizes on a Wombat with less alteration than I needed because the Wombat was a little wider here and there. Someone who has one may be able to say what they have used. If you can find stock sized trials tires there should be no fitment problems.

[hodakamax]

Hey Taz, I have the combination that AZ mentioned on my 94A 1973 Wombat. The front 80/100-21 is fine but the 100/100-18 back is close. I had to remove the chain guard to make it fit. Mine are rough knobbies and might be a little wider than the trials type. Some manufactures list dimensions on their website. They seem to vary by brand. Hope this helps!

Max

PS--I bought my last set from Paul at Strictly Hodaka and he was helpful to me on size selection and his prices were competitive.

[Dale]

Taz,
There are a number of good options for tires that will fit your Wombat just fine. If you want to stick with the original look of a trials tire check with Don at Allmototire.com. If you want a good all purpose tire, check out Shinko SR244. I run these 2.75-21 front and 3.50-18 rear. The Shinko SR244's are readily available. Knobbies are a bit tougher to size. If you want off-road knobbies check with Paul here at Strictly Hodaka or Don at Allmototire.
Dale

[taz]

Thanks for all the great info , I just found some real nice Kenda K 270 I'm going with the 4.00 18 for the rear and not sure if the front will be the 3.00 21 or the 3.25 21 ... Good deal at motocyclesuperstore with free shipping ...

[bchappy]

4:00 x 18 may be a little wide with the chain guard on. My experience with running without the chain guard is that you should never run a muddy race as the chain simply rubs the mud off the tire and packs it In the front sprocket area. A good way to wear out chains, sprockets and even bust up the rear of the engine. I remember one muddy cross country race where a guy thought his clutch was slipping and come to find out that all the teeth were gone off the rear sprocket and the chain was simply sliding around it (was not me). Also remember that the engine only has so much power and larger tires weigh more so it may slow down your acceleration instead of helping.

Just my two cents.

[Zyx]

When I raced my 100B (a long time ago in a county far, far away...) I could not mount a 4.00 x 18 because the swing arm tapers in at the pivot end and gets a lot narrower. A 3.50 was all that would fit, so I extended the swing arm to put the tire tread back in the wider part of the arm. This past year, to mount a 100/100, which in this brand is a 4 1/2 inch wide tire at the side knobs, I had to extend even further. The swing arm is now longer by 3 inches and braced on the bottom, and the tire clears on each side by no more than a quarter inch. Very tight.

Measure the width of your swing arm at the tread from nearest point of metal contact on each side. That's your target. Tire has to be narrower than that, and should be clear of the chain guard by a quarter inch more or less with the wheel dead straight. Clearance on either side may not be the same. Don't cock the wheel to make clearance.

[taz]

Ok with all the replies so far and looking at the stock sizes which are 2.75 x 21 front and 3.00 x 18 rear leaves a .25 difference front to rear .. After doing measurements I have thought to be safe would be a 3.25 x 21 front and a 3.50 x 18 rear ... Kenda K 270 ....

[Zyx]

Tires are rarely physically the size printed on the sidewall. So, a 3.50 tire may be nominally 3 1/2" wide, but this reference is most often the width of the carcass mounted on a stock size rim. The tread is wider. On a trials tire or streetable tire, that tread width is not much wider than the carcass. On a knobby, the tread is far wider than the carcass. Best bet is to go to your local motorcycle shop and look at typical tires, and measure them side to side with the bead held apart about an inch and a half to two inches. It won't be perfect, but it will be close.

Here is a photo of how far back I needed to move the tire to clear. You can see that the tread is now back where the arms bend toward the rear. Compare to your swing arm to get an idea of how the arm narrows, and go from there. You will probably be able to mount any 3.50 tire knobby or otherwise. 4.00 in a trials probably, knobby maybe. Just have to measure and compare.

[taz]

Just talked to Kenda and the 4.00 18 is max width of 4.1 inch so it will fit the Wombat with about 1/4 to 5/16 of an inch from chain guard ...