Best tyres for a 45?

[Panhead Boris]

Originally Posted by kevscrivener

however I could easily scrape both boards (including the mounting brackets) on mine, plus it went like the clappers,how much further do you want to lean?

I think that's the point of larger wheels? My pan used to scrape the boards like crazy on roundabouts. After fitting a 21" on the front no more scraping and higher speed thru bends...although it actually handles worse because of the skinny profile.

I would agree about Speedmasters, they are fine on older machines.

[45Brit]

4.00 x 18" wheels are the same nominal rolling radius as 5.00 x 16" , 18+8 = 16+10 = 26" diameter. This is assuming that the actual height of the tyre is equal to the nominal section, ( ie aspect ratio = 1 ) which it may not be for your actual tyre. Road Runners certainly aren't.

but they are lighter, so the unsprung weight on the front is less. The narrower section and higher pressure gives a more positive straight-line tracking effect and better response.


I have always felt that the 21" wheel was too narrow for the Big Twin, not least because of braking loads relative to the contact patch ( assuming you don't have a Glide front drum, in which case braking effects can be disregarded... )

21" rim is bigger though, but only by 1/2" on the rolling radius ( 21+6 = 27" ) .. although a 21" tyre usually has an aspect ratio of 1, so it may well make more difference in practice

21" wheels suit 45s better because they are lighter machines, quite a few British pre-war singles used 21" wheels in girder forks, although they were discontinued when teles were adopted because of clearance issues ( look at the late tele-fork Big twin Indians for an illustration of this )

[kevscrivener]

I suspect that for many of us the criteria will hinge on three things; looks, availability of parts and originality, not in any particular order.

I confess that I prefer the 16" for looks, excepting military bikes which of course would normally have the skirtless fenders.

Regarding brakes; I have some pics of a very neat set-up which I found some years ago down at Fred Warr's place. Bike belonged to one of the "45 Club" members who I think came from Portsmouth way.

Basically what he'd done was to hide a hydraulic master cylinder between the tanks, operated by a lever/cable on the right bar so no ugly bits on bars. This in turn operated a single disc on the front wheel, Jap I think but unsure of exactly what. The bike needed a disc to stop it 'cos shoehorned into that 45 frame was an Evo motor running a 5-speed box!


I'd love to post these pics but unfortunately my scanner's kaput at the moment; it was a VERY neat bit of kit.

Anyone got a pic of a 21" front wheel set-up on a 45 BTW, I'm curious as to how it would look?

[45Brit]

45 with 21" wheel looks like this!

why anyone would go to the trouble and cost of fitting an evo motor into a 45frame is a complete mystery to me... 45 frames are a purpose-built design to provide the minimum strength for the maximum weight! Was it a Big Twin sv frame? They are very similar in appearance, and people sometimes put panheads in them, for reasons best known to themselves.

the hidden master cylinder was done by BMW at one time for cosmetic reasons, but soon abandoned as more trouble than it was worth.