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gunner Offline OP
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My A65 uses an 18 inch rear wheel and I have always felt when riding that the rear end feels too low.

I was wondering if fitting a 19 inch rear wheel would improve matters and indeed what effect it would have on the handling.

My front wheel is 19 inch and I know most A65's used 19 inch front & 18 inch rear, although some models used 19 inch front and rear.

Also what range of 19 inch rear tyres are available?

All info welcome.


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I have A65's with 18" & 19" rear wheels. While tire selection is better for 18", I prefer the bike with 19" for riding. IMO, the bike with 19" just turns better. No hard data, but just the feel when riding.

Avon has RoadRiders for 19" rears, there are some other choices as well


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You can get the Duro HF308 in a number of sizes from 3.25x19 to 3.50x19 and 4.00x19.

http://www.motorcycletiresmaniac.co...8fhlh-MC0x7Dcw1v5tgI9YHaJuEyXhoCKqLw_wcB

http://www.oponeo.co.uk/moto-tyre/duro-hf308



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Hi,

Originally Posted by gunner
My A65 uses an 18 inch rear wheel and I have always felt when riding that the rear end feels too low.

Depends what tyres you have back and front - risking telling you something you know already, the "18 inch" or "19 inch" refers to the rim diameter - the 'ole in the middle of the tyre - not its overall diameter.

If you look at something like Avon's Roadrider page, you'll see the overall diameters of, say, 3.25x19 front and 4.00x18 rear are pretty much the same, despite the different rim diameters. As the overall sizes for each tyre section is at least guided by (non-)governmental standards organisations like ETRTO in Europe and US DOT, you can reckon on, say, a 3.25x19 from Dunlop, Bridgestone, etc. being a similar overall diameter to the Avon.

Originally Posted by gunner
I was wondering if fitting a 19 inch rear wheel would improve matters and indeed what effect it would have on the handling.

If the above tyre sizes are what your bike has and your "rear end feels too low", it's either in your head or the problem lies elsewhere (too-short/saggy Shocks.?); at least there's and easy fix for the latter. wink

Otoh, if you've believed some of the tyre makers' 'equivalents' (this Imperial size is 'equivalent' to that metric size) and have different sizes back or front ... laughing

Likewise, Jon's suggested 3.25x19, 3.50x19 and 4.00x19 will all have different overall diameters, even though the diameter of the 'ole in the middle is the same.

Nearly all Triumph and BSA triple models used both 19" front and back rims; they started out with a 3.25x19 front and 4.10x19 rear - 100/90x19 modern equivalent (and that is a close one); however, note that the 4.10 or 100/90 is narrower overall than the aforementioned 4.00, despite what the bald figures appear to indicate. cool

Just as an aside, indication and possible matter of interest, Conti are developing a 110/85x19 ClassicAttack radial rear for things like triples and Commandos, so it can be slightly wider overall than the recommended 100/90x19 front without having a greater overall diameter.

Originally Posted by gunner
what range of 19 inch rear tyres are available?

Small but pretty good; as well as the 100/90x19 Roadrider and TT100, there's also a 4.10x19 TT100 (and the aforementioned Conti rear radial?). Plus, doubtless weird square stuff like Avon SM's and the like ... eek

Hth.

Regards,

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Great info chaps, the tyres I'm using are rear Maxxis C907 120/90-18 and front is Maxxis C906 100/90-19. I have just measured the diameter of both tyres and they appear to both be approx 26 inches, so you are correct Stuart the overall diameter is the same despite different rim sizes. These tyres actually perform well despite the Chinese origin.

For info I'm using Hagon 2810 rear Shocks with the spring preload set so that the spring just start to sag when I sit on the bike. The Shocks are definitely correct length and I'm using progressive fork springs together with 20w fork oil.

In comparison, my B44 which uses 18 inch wheels seems to sit much higher at the back so I often wondered whether having wheels the same size would help.




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Err Stuart, I can't speak for triumph. But the A10's and afaik early A65 which had 19" F+R both used 3.50-19 on the rear.
My own question to this mix is,during the time when the 19" rear wheel was used, was BSA using 12.9" Shocks on the rear of the A65, or the 13.4" as used on the later PRE OIF models?


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Allan,

The 1966 A65L I took in 2 years ago has a Dunlop K70 4.00x19 on the rear. After dismantling some things, I am wondering if I was the first one to take it apart. But, in the U.S. I am pretty sure 4.00x19 and 4.00x18 were standard for rears on the 500's and 650's when running either 18" or 19" rims.

I will measure the Shocks on the '66 and let you know but they look like the standard 12.9" versions.



Originally Posted by Allan Gill
Err Stuart, I can't speak for triumph. But the A10's and afaik early A65 which had 19" F+R both used 3.50-19 on the rear.
My own question to this mix is,during the time when the 19" rear wheel was used, was BSA using 12.9" shocks on the rear of the A65, or the 13.4" as used on the later PRE OIF models?


Jon W.


1957 6T Thunderbird 650
1968 T100R Daytona 500
1971 TR6R Tiger 650
1970 BSA A65F 650
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Dry frame unit twins used 13.4" Shocks regardless of rear wheel size.


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Hi Allan,

Originally Posted by Allan Gill
the A10's and afaik early A65 which had 19" F+R both used 3.50-19 on the rear.

I was using the 3.25x19 and 4.00x18 sizes to illustrate my point that overall diameters are similar irrespective of the size of the 'ole in the middle. As "gunner's" posted later, his bike has similar-overall-diameter 100/90x19 and 120/90x18 and he's found them to be similar sizes. So the "low rear end" problem has another cause.

Btw, risking reiterating something you've remembered from previous discussions, 100/90 is a close dimensional equivalent to 4.10, which was introduced by Dunlop with the K81 as a direct replacement for 3.50, having similar overall diameter but greater overall (and tread) width.

So, if "gunner" were to replace his bike's 18" rear wheel with a 19", 100/90x19, 4.10x19, 3.50x19 and 3.25x19 would all give a similar overall diameter to the 120/90x18 his bike has now, but something like a 4.00x19 would have a larger overall diameter and steepen the effective steering angle a little.

Hth.

Regards,

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Something I forgot to mention is that the frame is actually from a 1962 A65 Star, whilst the engine is from a 1968 Firebird. I bought the bike as a box of parts and built it up to resemble a 68 Firebird.

The forks which came with the bike use the 8 inch sls brake and 19 inch wheel. I note from the 1962 A65 parts list that A65 stars used 18 inch front wheels with a full width brake. The rear wheel hub is the QD type with the brake on the left, so also not from an A65 Star which used a right hand brake and full width hub.

Whether this combination of parts makes any difference is anyones guess. As far an I know, there are only minor differences between an early A65 Star frame and later A65 frames.

I did wonder whether longer Shocks would help and when I spoke to Hagon they mentioned that standard length Shocks for A65 from 62 to 70 is 13.4 inches, which is what I have.

I looked at the 19 inch Duro HF308 tyre mentioned earlier and it does look interesting, however I noticed it's speed rating is 'P' - 94mph which is a little below an A65's max speed, not that I ever go over 80mph anyway smile

Last edited by gunner; 10/03/14 3:01 am.

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QD type swing arms are longer than FWH swing arms


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Quote
Whether this combination of parts makes any difference is anyones guess. As far an I know, there are only minor differences between an early A65 Star frame and later A65 frames.


Have you looked at the stanchions and yokes you have, dropped yokes have short stanchions to compensate so long stanchions in dropped yokes will lift the front end making the back seem low.

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When the A50 & A65 first came out in 1962 they had 18" front and rear wheels with 3-25 18" front tyre and 3-50 18" rear tyre. With the A50 having 7" front brake and the A65 having 8" front brake. This changed in 1964-5 for the US market the A50CC (US) having 3.25 19 front and 4.00 18 rear The A50C (UK) had front and rear 19" with 3.25 19 front tyre and 3.50 19" rear. The A65R had 18" wheels for 1964-5 whilst the A65L had 19" wheels for 1964-5. From 1966-70 the A50R had 19" wheels but the A50W 1966-7 had 19" front and 18" rear. The A65S 1966-8 had 19" front and 18" rear The A65H 1966-7 had 19" front and 18" rear. Then the A65FS-A65T- A65L- A65FS-A70L from 1968 all had 19" front and 18" rear the 1973 T65 had 19" front and 18" rear and all had 3.25 19 front tyres and 4.00 18" rear tyres with the exception of the A65FS which had a 3.50 19" front tyre.

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Originally Posted by photobob
with the exception of the A65FS which had a 3.50 19" front tyre.


And the US spec 70' lightning. For some odd reason.


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Hi Gunner,

My 64 Lightning Rocket has the 19" inch rims. It has the 3.25-19 K70 on the front and Made in GB 4.00-19 K70 rear. The handling is delightful. When these tires are done I will stick with the K70s and put the 3.50 on the back and keep the 3.25 on the front. If I was to try a different brand than the Dunlop I would put the vintage tread Heidenau on the bike.

Good luck.

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Yep, my '66 A65L does have 13.4" Shocks, thanks Rich B.

I measured the length of the upper shock covers on the 12.9's and the 13.4's and get 5 and 6 inches respectively.


Originally Posted by Rich B
Dry frame unit twins used 13.4" shocks regardless of rear wheel size.


Jon W.


1957 6T Thunderbird 650
1968 T100R Daytona 500
1971 TR6R Tiger 650
1970 BSA A65F 650
1955 Tiger 100 - Project
1971 BSA A65 650 - Project
1972 Norton Commando 750 "Combat"


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I know it is a BSA forum. but Norton ran 19" front and back on all of the Commando's. I haven't heard of anyone complaining about the handling.
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Hi Jeff,

Originally Posted by Jeff K.
Norton ran 19" front and back on all of the Commando's. I haven't heard of anyone complaining about the handling.

confused No-one's complaining about the handling here either.

Hth.

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Originally Posted by Stuart
Hi Jeff,

Originally Posted by Jeff K.
Norton ran 19" front and back on all of the Commando's. I haven't heard of anyone complaining about the handling.

confused No-one's complaining about the handling here either.

Hth.

Regards,


True, I have to say though I find the narrower rear tyre improves handling on a bike. I switched (on the 400/4) from the 4.10-18 TT100(K81) to a 3.50-18 K82 which is fractionally narrower and slightly bigger circumference and it made the bike a lot more flick able in corners. It would be interesting to see if it has the same effect on the A65, switching out the 4.00-18 to the 3.50-19 wheel.


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Stuart,
If you go to a 19" wheel I believe a different speedo drive will be needed. You can check this in a 66 parts book. The 66 BSA East Coast version had a 19 inch rear wheel, while the West Cost versions had 18.

I have a 66 EC T Bolt with 19 F 19 R and 64 LR with 19 F 19 R. What I found odd is the 64 seems to sit lower than the 66 and the 64 is the best handling of my three bikes. I caulked up to the dropped triple clamp on the 64

Good luck,
Richard

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Thanks for all the replies, I'm now seriously considering changing the rear rim from 18 to 19 inch in combination with 4.00-19 tyre, probably a Heidenau K34 which seems to get good reviews and is readily available.

I suppose my only issue is whether the front Maxxis and rear Heidenau tyres would be compatible.

Looking at the front Maxxis, it mentions it's size in imperial is 3.25-3.50 19 inch, so size wise seems OK. On the tyre itself it says it has 4 sidewall plies and 2 tread plies, so not sure if this a cross ply or radial tyre and if it will work with a Heidenau?


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Why not just get a Heidenau K34 front to match your rear and make it easier on yourself and be done with it ?

I'm sure you are already aware but for the others to see, this is from the Heidenau site:

K34 Vintage Motorcycle Tire

Heidenau K34 Vintage Motorcycle Tire Sizes:

3.25 – 18 M/C 52S TT
3.50 – 18 M/C 62S TT
3.25 – 19 M/C 54H TT
3.50 – 19 M/C 57H TT
4.00 – 19 M/C 64H TT

http://heidenautires.com/vintage-motorcycle-tires/




Originally Posted by gunner


I suppose my only issue is whether the front Maxxis and rear Heidenau tyres would be compatible.



Jon W.


1957 6T Thunderbird 650
1968 T100R Daytona 500
1971 TR6R Tiger 650
1970 BSA A65F 650
1955 Tiger 100 - Project
1971 BSA A65 650 - Project
1972 Norton Commando 750 "Combat"


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gunner Offline OP
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Agreed, I will put Heidenau on the front as well for compatibility and looks.


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Hi Richard,

Originally Posted by Richard Phillips
If you go to a 19" wheel I believe a different speedo drive will be needed.

Nope. Look at the overall diameters of, for example, the 4.00x18 and 3.50x19 K70 or the 4.00x18 and 100/90x19 (very similar to 3.50x19) Roadrider. Same or very similar overall diameters. As I wrote in my first post to this thread, overall dimensions for given tyre sections (the figures you see on the sidewall) are mandated by external organisations, so certainly the overall diameters of any 4.00x18, 100/90x19, 4.10x19 and 3.50x19 will be very similar, irrespective of the tyre maker.

Originally Posted by Richard Phillips
You can check this in a 66 parts book.

Look again at the parts books: same speedo. head and drive ratios irrespective of whether the variant was fitted with an 18" or 19" rear wheel. If you look also at any separate UK-market parts book, you'll find both BSA and Triumph used the same speedo. heads and drive ratios even though they fitted smaller tyres to UK-market bikes; the variation in overall diameters is well-within any accuracy range stipulated by any country's laws.

Hth.

Regards,

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Hi,

Originally Posted by gunner
not sure if this a cross ply or radial tyre

Except for ContiClassicAttack, no radial tyres in sizes to fit our old heaps. smile

Hth.

Regards,

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