18 inch wheels front and rear

What's your thoughts on 18 inch wheels, front and rear? Me well I think 19's front and rear look weird and probably don't help in the handling department and also when shopping for a 19" rear tire our options are kind of limited . Next year I'm probly going to have 18 inch wheels laced up.

The Commando's were design for 19" wheels and not sure why you think they look weird and as going to 18" would not be much more difference, as for handling my Commando handled good , even before converting to the Featherbed frame I still kept with 19" rims but laced to Akront Alloy rims and as tyre choice the Avon RR are a pretty good choice of tyres get good life out of them and handle pretty good even in the wet, I also ran Avon RRs on my 2013 Triumph Thruxton, if you think changing to 18" rims if you are having handling problems then may be something else is wrong as I still have a few friends with stock Commando's and they don't have any problems with handling, but a few have gone to alloy rims in stock 19" sizes.

Ashley

Jackman said:

What's your thoughts on 18 inch wheels, front and rear? Me well I think 19's front and rear look weird and probably don't help in the handling department and also when shopping for a 19" rear tire our options are kind of limited . Next year I'm probly going to have 18 inch wheels laced up.

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I think the front will look weird with 18" unless you plan to do something different with the front fender. 19" front, 18" wider rear is common on some vintage British twins, just not Norton.

Most Triumph twins had WM2-19 front and WM3-18 rear with 3.25-19 or 3.50-19 front tires and 4.00-18 or 4.25-18 rear tires - they don't look weird.

They ran 23 in front & 21 in rear , once . So they didnt fall in potholes so easilly .
With the New Austrailian Govt. initative , POT HOLES have made a comeback ,
so the large wheels may well do too .

Pre Unit T120 , 61 , came to me with 18s F & R . I changed em to 19s . Crankier on these in many ways .
The Steering on 18s was less fussy perhaps .
Do the Ducati 750 Sport & S uper Sport run 18's . Thingo's did !!

TOURING , Id go to a 16 rear & keep the 19 Front .

Think the period Laverda's ran 18's too , so al may not be lost .

With new rims being in short supply here, I laced up a set of front and rear 18" wheels for a customer's Commando a few weeks back - WM2 x 18 front, WM3 x 18 rear. Must have cost a pretty penny for these wheels - all new parts (including hubs). Looked nice - would be interested to see them on the bike.

Jackman said:

What's your thoughts on 18 inch wheels, front and rear? Me well I think 19's front and rear look weird and probably don't help in the handling department and also when shopping for a 19" rear tire our options are kind of limited . Next year I'm probly going to have 18 inch wheels laced up.

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I run 18 " wheels back 110/90 and front 100/90 both on 2.15 rims. It handles well and just LOVES going round corners. As far the front guard is concerned, I have a Ducati 38mm forks fitted so I use a Std Ducati 18" front guard. But the whole thing works for me. Even Norman White in his Commando Restoration Manual recommends going to 18 " wheels. Brett

So, just put 18” F&R using 100/90 and 120/80 BT46 Battalax as per Norman White’s recommendation. Front’s a 3 spoke dymag , rears a modified GPZ750 wheel giving Cush drive, solid axle and disc . looks good for me so end of.

Few test runs and things didn’t feel right…used the 30/34 psi as recommended…tried variations with suspension etc but not stable n ponderous cornering…rang Bridgestone, got lucky as bike tyre specialist answered…pressures now 36/42 …massive transformation, way better than Avon am26 r/riders IMHO.

Modern tyres run higher pressure than tyres of old.

I had 19s front and back on my Featherbed Triton. I changed them to 18s to get better rubber. The only difference I noticed, was where the handling was nimble, the bike made me exhausted. I used to get off the bike after a 5 lap race, absolutely buggered. And the bike was no faster with the better rubber. When you reduce the trail, you increase the angle of lean of the bike in corners. Theoretically you should be able to ride faster, but you are usually faster when the bike is more upright. You can put power on the ground better.

B

Rosey said:

I run 18 " wheels back 110/90 and front 100/90 both on 2.15 rims. It handles well and just LOVES going round corners. As far the front guard is concerned, I have a Ducati 38mm forks fitted so I use a Std Ducati 18" front guard. But the whole thing works for me. Even Norman White in his Commando Restoration Manual recommends going to 18 " wheels. Brett

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Sounds like a nice set up , good to hear it helps with the curves that's a big part of my goal . I'll check out Ducati guards too might work with Commando forks and guard work hmmm .

Most of us racing Commando frames here in New Zealand go to 18" rims to get a better choice of tyres.
I run 110 on the front and 130 on the rear for the race bike (Avons with race compound) the rear is a cantilever item that suits the narrower rims as we are limited to certain rim widths racing the Classics. I am thinking of going to an 18" rim on the rear of my Roadster for the same reason, happy with the 19" front as it gets along a lot of gravel roads from time to time .

Is the total diameter the same with the 18 inch as the 19 inch when you measure it at the tyre?

Onder said:

Is the total diameter the same with the 18 inch as the 19 inch when you measure it at the tyre?

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Depends on the tyre and manufacturer. My AM26 are the same rolling diameter 100/90-19 front and 4.0-18 rear.

Brooking 850 said:

Most of us racing Commando frames here in New Zealand go to 18" rims to get a better choice of tyres.
I run 110 on the front and 130 on the rear for the race bike (Avons with race compound) the rear is a cantilever item that suits the narrower rims as we are limited to certain rim widths racing the Classics. I am thinking of going to an 18" rim on the rear of my Roadster for the same reason, happy with the 19" front as it gets along a lot of gravel roads from time to time .

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You would probably find most of their featherbed frames have 60 degree rake. Ken Mc Intosh's Molnar which Cameron Donald rides has 19 inch wheels and I suspect 54.5 degree rake. The original Manx had very short offset fork yokes . When I fitted 18 inch wheels to my Triton, it buggered the handling and it would have cost too much too make the backwards step.
I probably would not matter much if you did it to a road going Commando, because you don't need it to be nimble in corners.

Brooking 850 said:

Most of us racing Commando frames here in New Zealand go to 18" rims to get a better choice of tyres.
I run 110 on the front and 130 on the rear for the race bike (Avons with race compound) the rear is a cantilever item that suits the narrower rims as we are limited to certain rim widths racing the Classics. I am thinking of going to an 18" rim on the rear of my Roadster for the same reason, happy with the 19" front as it gets along a lot of gravel roads from time to time .

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If you run much softer springs in the rear, and you wind the throttle on the back goes down more and your bike usually goes towards more oversteer - which is better for accelerating around corners staying more upright.
When you fit 18 inch wheels, everything gets closer to the road. I shortened the footrests and still managed to lift the rear wheel in a corner. I threw the bike upright by grabbing the frane rail and a really big tank slapper happened. I had hold of the tank and when the tank slapper looked as though it had stopped, I grabbed the handle bars. That is when I got launched over the front.
Theoretically the bike should be faster with better rubber and more lean, but it isn't.
I was really amazed when I rode an original 500 Manx. It was so much better then my 500cc Triton - slower but faster. If you got off-line, you just gave it more stick. That Manx was owned by Ginger Molloy and brought to Australia by my mate. It went to Western Australia, and is now back in New Zealand, restored back to very original condition. The guy who owns it is well known . Ken McIntosh knew who he was.

acotrel said:

You would probably find most of their featherbed frames have 60 degree rake. Ken Mc Intosh's Molnar which Cameron Donald rides has 19 inch wheels and I suspect 54.5 degree rake. The original Manx had very short offset fork yokes . When I fitted 18 inch wheels to my Triton, it buggered the handling and it would have cost too much too make the backwards step.
I probably would not matter much if you did it to a road going Commando, because you don't need it to be nimble in corners.

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As has been said before, Molnar Manx frames are to factory drawings. As are his yokes. I’m pretty sure the same it true for Ken’s stuff.

Molnar strongly recommends 18” wheels.

So 18” wheels work very well with standard Manx frames Al.

I do wish you’d recognise this.

Fast Eddie said:

As has been said before, Molnar Manx frames are to factory drawings. As are his yokes. I’m pretty sure the same it true for Ken’s stuff.

Molnar strongly recommends 18” wheels.

So 18” wheels work very well with standard Manx frames Al.

I do wish you’d recognise this.

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Molnar Manx Nortons probably have 60 degree rake on the steering head as do most after-market featherbed frames these days. They probably also have less yoke offset compared with a Commando. An original Manx has 54.5 degree rake and about 2.25 inch of yoke offset and comes with 19 inch wheels. The bigger the wheels, the more trail you have. The shorter the yole offset, the more trail you have. On an original Manx, the 54,5 degree rake decreases the trail. But it all balances out to become a very nice handling bike. A similar result can be achieved with 60 degree rake, 2.25 inch yoke offset, and 18 inch wheels - which is probably what a Molnar Manx has. When you fit 18 inch wheels in place of 19 inch wheels on a bike without changing the rake or the offset, you decrease the trail. Reduced trail causes understeer, both going into corners and coming out of corners. It also increases the lean of the bike in corners.
The increased lean means you need better rubber, but better rubber is the reason you fir 18 inch wheels in place of 19. If you had better rubber with 19 inch wheels and not 18 inch, you would be much faster in corners, because the bike stays more upright and tends to oversteer, so yo can gas it much harder in the corner.
Ken McIntosh uses Molnar motors in featherbed frames with 19 inch wheels. I would almost be certain his frame rake would be 54,5 degrees. And his fork yokes would be the old Manx offset of 2.25 inch. Commando fork yokes have more offset than Manx yokes, Molnar or original. So less trail and when you fit 18 inch wheels you reduce the trail even further.
All that happens is the bike becomes stiffer, leans more and does not turn so easily. Which on a road bike might be good - OR NOT.

When I fitted the 18 inch wheels to my featherbed Triton, they stuffed the handling. I was so bloody disgusted. I used to get off the bike after races, exhausted. And the bike was not much faster, I just had to work harder to do the same speeds.

Al please give some kind of evidence for your ‘probably’.

I’ve spoken to Molnar, have you?

His frames are to factory drawings.