Tyre sizes again
- Thread starter Flo
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Flo, I know the smaller front diameter should make it a little easier to turn but IME the 100 section on the front will tend to make it harder. I haven't used an 18" front but the 100 with a 19" was a lot harder to get on it's side than the 90 90 I've just gone back to. I have a 110 90-18 rear.
I think the answer lies in matching the tyres to the rim width. If you are having new rims laced on, look at what tyres you want to use and choose the rim size to suit. Believe me, a 100/90 Roadrider on a 2.5" rim does NOT make for heavy steering. There have been some long discussions on this and there are some wide variations in favoured options, however, IMO, forget the looks and go for something that works, which again comes down to matching tyres to the rim widths.
I have WM3, 18" rims on both wheels. Been using 110 x 90 rear & 100 x 90 front, but does not handle at high speed.
Now on 110 x 90 both wheels, does handle, but don't like the feel of it or the looks.
The 2 options are WM4 on the back with 120 x 80, & 100 x90 front. Or WM2 x 19 on the front with a 90 x 90 tyre.
I like the 1st option but it lowers the front of the bike 6mm, may need a spacer on fork spring to pull bike up straight?
2nd option will work as keith has proved.
I posted about the 1st option, wondering if anybody here actually uses it.
I am inclining towards the 19" front wheel, presume it is good at high speed.
Now on 110 x 90 both wheels, does handle, but don't like the feel of it or the looks.
The 2 options are WM4 on the back with 120 x 80, & 100 x90 front. Or WM2 x 19 on the front with a 90 x 90 tyre.
I like the 1st option but it lowers the front of the bike 6mm, may need a spacer on fork spring to pull bike up straight?
2nd option will work as keith has proved.
I posted about the 1st option, wondering if anybody here actually uses it.
I am inclining towards the 19" front wheel, presume it is good at high speed.
Flo, do you mean it's hard to turn at higher speeds, above 70 or some other handling characteristic ? If the first then the 90 should help but strictly speaking it should be on a WM3 although originally I used a WM2 steel and that made for a pronounced curve to the tread possibly making it more twitchy at low speed. With a lowered front end it typically makes the bike quicker to turn as it steepens the head angle and reduces trail. I'd think the larger rear (120) might slow it down. Of course many will say the standard 100 90-19 front and rear is the best. I think even with this set up which was on the bike when I first bought it I remember having to muscle it around at speed.
Here is the problem. Years ago I fitted WM3 18" rims front & rear.
Fitted Avons, 110 x 90 rear & 100 x 90 front, from then on it weaved at anything over 75mph & got worse the faster I went,
long sweeping bends were a disaster.
Then fitted Bridgestone BT45's the same size, hell of a lot better, but still the same problem, but to a lesser degree.
Recently fitted a 110 x 90 front & cured the problem, but I don't like the feel of it or the looks.
Seems that a lowered front end wrecks the handling. Two up, it is always perfect.
Norman White suggests 120 x 80 x 18 rear & 100 x 90 x 18 front.
Mick Hemmings suggests 110 x 90 x 18 rear & a WM2 x 19 front rim (didn't say tyre size, but a 90 x 90 seems good).
So if I go for a 19" rim, would a WM3 be better than a WM2.
I want to get this right as I am fed up with messing around with it, & I don't like poodling around.
Fitted Avons, 110 x 90 rear & 100 x 90 front, from then on it weaved at anything over 75mph & got worse the faster I went,
long sweeping bends were a disaster.
Then fitted Bridgestone BT45's the same size, hell of a lot better, but still the same problem, but to a lesser degree.
Recently fitted a 110 x 90 front & cured the problem, but I don't like the feel of it or the looks.
Seems that a lowered front end wrecks the handling. Two up, it is always perfect.
Norman White suggests 120 x 80 x 18 rear & 100 x 90 x 18 front.
Mick Hemmings suggests 110 x 90 x 18 rear & a WM2 x 19 front rim (didn't say tyre size, but a 90 x 90 seems good).
So if I go for a 19" rim, would a WM3 be better than a WM2.
I want to get this right as I am fed up with messing around with it, & I don't like poodling around.
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- Mar 30, 2008
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I think I've posted this notion before, but I prefer a 19" in the front and an 18" in the back.
The 19 front for two reasons. First, if I'm not using the bike for racing, the 19 seems more stable and tractable on the street. Second, most original style and some of the newer front fenders are built for the 19" radius. 18's make original fenders look a little weird. As for the 18 rear, I can find a lot more tires for the 18" rear and can match the final diameter of the front and rear through careful selection of tire sizes. I prefer a wider 18" rim to accommodate the wider tires.
I have 19's front and back on my Manx because the AHRMA rules require them. However, I find that the bike handles fine and like the high speed stability of the 19's. I'm building a Triton and have the wheels already built. WM2 19 front and 2.75" 18 rear. I plan to run an Avon 90/90-19 front and a 180/80-18 rear. Diameter of each is close to 26".
The 19 front for two reasons. First, if I'm not using the bike for racing, the 19 seems more stable and tractable on the street. Second, most original style and some of the newer front fenders are built for the 19" radius. 18's make original fenders look a little weird. As for the 18 rear, I can find a lot more tires for the 18" rear and can match the final diameter of the front and rear through careful selection of tire sizes. I prefer a wider 18" rim to accommodate the wider tires.
I have 19's front and back on my Manx because the AHRMA rules require them. However, I find that the bike handles fine and like the high speed stability of the 19's. I'm building a Triton and have the wheels already built. WM2 19 front and 2.75" 18 rear. I plan to run an Avon 90/90-19 front and a 180/80-18 rear. Diameter of each is close to 26".
Had that same characteristic 'Commando weave' at 75+ and put up with it for years, snaking I call it. Tried improving wheel alignment by twisting the rear with the adjusters but minimal improvement. Reading the Phantom oiler piece got me thinking and while I didn't go the whole way with redrilling mounting holes I did find my front mount was offset differently from the cradle by 0.060". The tube was welded too far left and with bare cases I had to force the assy to the right to fit the mount (Norvil vernier). With an assembled engine it was more difficult and the weight masked the problem since a fair bit of manipulation was needed anyway. Effectively the whole engine and swingarm assy was pointing left which is where the bike steered naturally. Cutting 60 thou off the right hand end and adding a spacer to the left allowed the mount to slip in a treat, even with an assembled vernier. I didn't really expect that would be the whole answer so I took a lot of care to get the rear aligned with the front by tweaking the spokes. Result, no more weaving in a straightline at speed. As for long high speed bends it doesn't feel as planted as it could be but I think that's down to the loose standard (010") Iso clearances I run.
I know some bikes are sensitive to tyre choice but IME with three different tyres and sizes the 'weave' was always there. It is possible to measure the cradle offset on the bike but you have to remove the Iso caps, not so easy if you have verniers.
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