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#517479 - 12/05/13 4:30 am Re: Largest rear tire for a Thunderbolt [Re: ]  
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Pete R - R.I.P. Offline
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Why would you change to 16"?
Most 16" tyres are far too wide.If you offset the rim to clear the chain and chainguard,the bike will always steer itself left.

It may be economical,because a wider tyre lasts longer.It won't be good for grip or handling.

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#517493 - 12/05/13 7:02 am Re: Largest rear tire for a Thunderbolt [Re: ]  
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Stuart Offline
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Hi,

Originally Posted By: Thunderbolt69
I have a 69 thunderbolt.

Front: Akront 19 x 2.15 rim with Avon Speedmaster MK11
Rear: Akront 19 x 3 rim with Avon Roadrunner 100/90/H19 tyre
Looking at you picture, I'm guessing you mean WM2 ("2.15") and WM3 ("3")? A 3.00 rim would be enormous.

Originally Posted By: Thunderbolt69
I will be changing to a 16'

What tyre size are you considering with that rim? Wider tyres need exponentially-increasing amounts of time and work to fit to Brit. bikes because they were never designed for 'em. Fit a narrower tyre and the back drops because the tyre width (so height) can't compensate for loosing 2" or 3" from the rim diameter.

Hth.

Regards,

#517543 - 12/05/13 1:39 pm Re: Largest rear tire for a Thunderbolt [Re: Thunderman]  
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No Name Man Online content
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If you are interested in handling, I personally wouldn't recommend a fat rear on a 16" wheel. They look pretty good on bobbers if that's what you are after. A 19" won't necessarily hurt your handling but it isn't easy to find a modern 19" rear tire. At least I haven't found one. 19" modern front Dunlap on rear of my A10 (rotating backward...because someone decided that is better I guess). I plan on replacing that with an Avon for better overall stick and feel.
Anybody know who decided to turn a front tire around on the rear and have experience with both directions?
If it were my Thunderbolt I would get an 18" wheel.

Bill


69 A65T
71 B50T
85 K100RS
54/59 A10SR
69 B44VS
71 A65FS
Too much moderation is bad for you.

#517544 - 12/05/13 1:51 pm Re: Largest rear tire for a Thunderbolt [Re: Thunderman]  
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kommando Online content
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Scotland
Tyres are not a fashion item, going bigger is not always better. Those 2 thin strips are you only contact with earth so treat it so and fit the tyres that give the best handling and not looks.

#517553 - 12/05/13 3:04 pm Re: Largest rear tire for a Thunderbolt [Re: Thunderman]  
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Best handling is most important for me also, as I tried to imply to Tbolt69.
As far as Thunderman's question is concerned, I haven't mixed a K70 front or rear with a modern on the other end but I would assume both ends modern would suit me better than a mix. I am also sure all moderns are not alike. I am not particularly thrilled with the modern Dunlaps on the A10 and Gunner says he likes his Chengs fine...
For on-road handling a narrower tire probably will work better on the front. 100-110 mm. The 120 Avon rear has exceptional handling to me.


69 A65T
71 B50T
85 K100RS
54/59 A10SR
69 B44VS
71 A65FS
Too much moderation is bad for you.

#517597 - 12/05/13 9:57 pm Re: Largest rear tire for a Thunderbolt [Re: No Name Man]  
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gunner Online content
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Farnham, Surrey, UK
I agree, and for good handling, its best not to mix old style and new tyres. IM using a cheng sing C906 front in size 100/90 19 in combination with the C907 cheng sing rear, which seems to work well.

IM not searching for originality on my bikes, just good handling and performance, hence the use of modern components not just limited to tyres.

Last edited by gunner; 12/05/13 9:59 pm.

1968 A65 Firebird
1967 B44 Shooting Star
1972 Norton Commando
#517601 - 12/05/13 10:12 pm Re: Largest rear tire for a Thunderbolt [Re: No Name Man]  
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Stuart Offline
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Hi Bill,

Originally Posted By: No Name Man
A 19" won't necessarily hurt your handling

It won't. All triples except Hurricanes (arguably the worst-handling triple) have 19" back and front.

Originally Posted By: No Name Man
it isn't easy to find a modern 19" rear tire.

What's not modern about Avon Roadrider? Or plenty of triple owners are still happy with TT100's. A '69 Thunderbolt isn't going to trouble either. smile

Originally Posted By: No Name Man
front Dunlap on rear of my A10 (rotating backward...because someone decided that is better I guess).

The strip of rubber that's becomes the tread during moulding has an overlapping joint. Years ago, the tyre makers considered that the overlap should be orientated one way when braking forces were highest (front tyre) and the other way when acceleration forces were highest (rear tyre). These days, they aren't bothered so much.

Originally Posted By: No Name Man
For on-road handling a narrower tire probably will work better on the front. 100-110 mm.

I don't believe you've any chance of fitting a 110-width between the fork legs. On my '70 T150, I have to deflate the 4.10 (100/90) TT100 to get it past the mudguard (fender) mountings, or remove the 'guard/fender and mountings.

Also, while a 4.10 will under a Triumph 'guard/fender, it won't under a '69 R3 one. Some reckon Small Heath modified the '70 R3 'guard/fender brackets, but there were/are so few '70 R3's in total, never mind with an original TT100, it's hard to be sure.

Back in the day, post-launch testing and production racing established that the triples handled better with a 4.10 (100/90) front tyre to the extent that the fitting hassle was worth it; otoh, all the twins stuck with a 3.25 - which is narrower - 'til the Co-op fitted 4.10 fronts years later.

Has to do with how much weight the different bikes are putting on the front tyre contact patch; if you're ... uh ... well-built ... and ride leaning well-forward, you might make up for lower weight a twin puts on the front. wink

Hth.

Regards,

#517686 - 12/06/13 3:56 pm Re: Largest rear tire for a Thunderbolt [Re: Thunderman]  
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Stuart, the few places I have looked don't have an Avon R-rider or R-runner in 120-90-19. What is your source? In fact, they told me no 19" rear tires. Would like one...
I had a 110-90-18 R-runner on the front of the 69 Tbolt. Did have to deflate it to get it on but had plenty of clearance once in there. Wore it out. Handled great. Now a 100-90 R-rider. Also handles great. Not much difference on my A65 between em. A little quicker turn in with the skinnier. And easier to get on.
Wish I had an R3 or Trident to try different tires on!
Belatedly looked at the link you provided but don't see a 120-90-19 rear...
Bill


69 A65T
71 B50T
85 K100RS
54/59 A10SR
69 B44VS
71 A65FS
Too much moderation is bad for you.

#517688 - 12/06/13 4:13 pm Re: Largest rear tire for a Thunderbolt [Re: Stuart]  
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Gnashville
Originally Posted By: Stuart
if you're using 100/90 rear, 90/90 front is a widely-used combination by many bike makers.

Regards,

I am, and it works very well, thank you!
Granted, there is a bit of a gap between tire and fender on the front, but I'll live with that for good handling any day! grin


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
#517696 - 12/06/13 5:22 pm Re: Largest rear tire for a Thunderbolt [Re: No Name Man]  
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Stuart Offline
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Hi Bill,

Originally Posted By: No Name Man
the few places I have looked don't have an Avon R-rider or R-runner in 120-90-19.

You won't.

Risking stating the obvious, bear in mind that the distance between the axle and the ground is made up of the hub, the spokes, the rim and the height of the tyre cross-section. If that height is 90% of the width, that would make for an absolutely huge overall diameter. So, if you're increasing the rim diameter by an inch, you must be doing something else to reduce the height of the tyre cross-section; if the height is a percentage of the width, and you want to reduce the height, you must be reducing the width?

So, repeating the Avon Roadrider webpage link (shame I don't get a cut frown ), if you want a tyre on 19" rim with a similar axle-ground distance to a 120/90x18, you're looking at a 100/90x19 ... which, coincidentally, is the metric equivalent of 4.10x19, which is what most triples were fitted with originally ...

Originally Posted By: No Name Man
In fact, they told me no 19" rear tires.

They're being obtuse. frown They clearly don't need your money so, in your position, I'd be inclined to take my money to someone who actually wants to help me buy something ...

There aren't any 'rear-only' (as in the opposite of 'front-only') 19" tyres. But there are 'univeral' tyres, that can be fitted to both rear and front (reversing the direction of rotation as I explained in my previous post) - as well as at least half-a-dozen different Roadrider sizes, so are the TT100's, the 3.50x19 K70 and probably other etc. from other makers ... you get the picture?

Originally Posted By: No Name Man
Would like one...

No, you wouldn't ... the bike would look silly and handle like a pig on stilts ... grin

Hth.

Regards,

#517714 - 12/06/13 6:53 pm Re: Largest rear tire for a Thunderbolt [Re: Thunderman]  
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Well, you may be right about that. Don't want a universal tread particularly. Not sure about the looking silly part and pig-handling part...the Dunlap I have on there isn't doing it for me so I will try something else eventually.

Bill


69 A65T
71 B50T
85 K100RS
54/59 A10SR
69 B44VS
71 A65FS
Too much moderation is bad for you.

#517718 - 12/06/13 7:50 pm Re: Largest rear tire for a Thunderbolt [Re: No Name Man]  
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Stuart Offline
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Hi Bill,

Originally Posted By: No Name Man
Not sure about the looking silly part and pig-handling part

If you look at original tyre sizes, and then their outside diameters on something like the Avon web pages, you'll see that, for all the different numbers moulded on to sidewalls, all the tyres had/have pretty similar outside diameters. Even when BSA (and Triumph) fitted smaller wheels/tyres to 'UK & General Export' variants, the relationship between the two wheels was maintained.

If you put a wheel with a larger o.d. on the back, because the whole bike then rotates around the front axle, you steepen the steering angle. Steepening the steering angle reduces the self-centering effect on the steering, interpreted by some as 'quicker steering' but experienced by others as a greater liking for wobbles (up to tank-slappers frown ). Ok, I might've been exaggerating the effect on the looks of a larger o.d. rear wheel but, ime, it takes very little change in steering angle to make a big change in the feel of the bike on the road. By all means try it, ime just be careful what you wish for. whistle

Hth.

Regards,

#517807 - 12/07/13 1:27 pm Re: Largest rear tire for a Thunderbolt [Re: Thunderman]  
Joined: Aug 2006
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No Name Man Online content
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Understand what you are saying Stuart...may well end up with the lower aspect but my A10 isn't stock. Slightly low in the back. Side stand contacts before peg now. The slight amount of height increase we're talking about will help there. Coupled with a stickier front Avon I think it will handle at least as well as it does now. I will let you know...

Bill


69 A65T
71 B50T
85 K100RS
54/59 A10SR
69 B44VS
71 A65FS
Too much moderation is bad for you.

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