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Post by brokenicarus on Mar 17, 2007 14:04:50 GMT -5
Hey all, My tires are pretty hard and cracked, i'm thinking new ones are definitely in order. I know Stew and some other guys recommend BT45's, I'm thinking about getting those, but I don't know much about tire sizing. My rear is a Dunlop Roadmaster, it says 4.25 85 H18 on it, my front's a bridgestone 3.50 S19. I know this much: the H and S are speed ratings, right? and the 18/19 rim diameter? is the other number a ratio between hight and width? how do I know what fits or not? Is it like a bike tire, where pretty much anything's ok?  Oh, and I'm running tube tires. Can I put on tubeless? and finally, where do I get new tires from? I don't need anything fancy, just for 'round town fun. Thanks, sorry for the barrage of oft'-answered questions. Davey |
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Post by milkman on Mar 18, 2007 7:02:50 GMT -5
I run the BT45's, couldn't fault them.
You can't run tubeless tyres unless you get rims that will accomodate them. The spokes are on the inside of teh wheel and hence not entirely conducive to keeping air in.
Even if its around town mate, better off getting something with decent grip like the BT's. Putting around town is more where you'll need teh grip when you hit the anchors for a walker, cyclist, idiot driver etc than out on the road.
Thats my two cents anyway.
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Post by milkman on Mar 18, 2007 7:04:30 GMT -5
Sorry, forgot you might have the cast alloy wheels, and hence no "spokes" as I was reffering too.
Still, I wouldn't run tubeless on a wheel not designed for it.
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Post by brokenicarus on Mar 18, 2007 10:39:23 GMT -5
hey thanks mate, cast wheels I have. But they still want tubes huh? I'll probably be getting the BT's, now I just have to track em down
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Post by colinjay on Mar 18, 2007 16:29:13 GMT -5
Hi,
Not all cast wheels are suitable for use as tubless rims/tyres. The cast wheels that were firred to the 1978 SR500E ARE NOT suitable for use with tubless tyre as they do NOT have the correct rim profile. I think the correct type of rim is designated as a CM profile?
To use tubeless tyres, the rim profile MUST have a safety rib that prevents the tyre comming off off the "sholder" of the rim and dropping into the rim well if it deflates. You can fit tubless tyre to the SR rims, but if you have a tyre deflate, it can actually come off of the rim, which is not real good for your high speed handling.
I would sujest that you have someone check the rim profile before fitting tyre with out tubes!!
CJ
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Post by StewRoss on Mar 18, 2007 17:04:02 GMT -5
Hi, Colin I agree with you totally...it's not good at all if a tyre comes of the rim as it deflates...definitely use tubes with these rims. SR |
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Post by colinjay on Mar 19, 2007 16:31:50 GMT -5
Hi again,
Last night I went through my collection of tech article, but could not find the one that give the rim type that are designed for tubless tyre.
However, I had a look at some of the wheels I have in my shed and a mid 80's Honda rim from a CBX750 (Nighthawk) that I have has a tubeless rim. This rim is marked MT215x16, the MT is the rim profile and this is one of about 3 tubeless rim profiles. I would recommend looking at the manufacturers markings on an alloy wheel, and if it does not have a "profile code" such as MT on it, not to fit tyres without a tube.
You can still fit tubeless tyre, but you have to run a tube in them.
CJ
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Post by miker on Mar 20, 2007 9:35:59 GMT -5
In the US, the 78/79 came with cast non-tubeless wheels, and the 80/81 came with cast tubeless wheels (just like the XS650.) I think the tubeless-compatible wheels actually have "Tubeless" cast into one of the spokes.
miker
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Post by hopwheels on Mar 20, 2007 14:11:56 GMT -5
You know, I can't seem to find this anyhere here, but I'm probably not looking hard enough. So the stock tire sizes on an SR are 400x18 rear, and 350x19 front I think. How does that translate into current tire sizing? I'm looking at the BT45's as well, and I'm finding in a 19's 100/90 V-19, and 110/80 H-18, 100/90 H-18 in 18's, etc., etc. What is the definitive, ideal tire size for the 2.15x18 rear rim and 1.85x19 front rim in the BT45's? Thanks!
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Post by colinjay on Mar 20, 2007 22:10:34 GMT -5
Hi,
The tyre size conversion chart below was copied from the Continental Motorcycles web site. It should give you a basic idea of how the sizes convert.
metric inch alpha
80/90 2.75, 3.00 (MH 90)
90/90 3.00, 3.25, 3.60 MH 90
100/90 3.25, 3.50, 3.60 MJ 90
110/90 3.50, 3.75, 4.10 ML 90
120/90 4.00, 4.25, 4.25/85, 4.60 MN 90, MP 90
130/90 4.50, 5.00, 5.10 MT 90
140/90 5.50 MU 90
Somewhere at Home I have a chart that lists what size tyres are correct for the various rim sizes, I will see if I can find it. The basic rule of thumbs has been, that you can fit one size either side of the std fitment tyre, i.e. if the std tyre was a 4.00 on the 2.15 rim, you could fit a 3.50 or a 4.50, without any real problem.
CJ
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Post by wotavidone on Mar 21, 2007 0:25:21 GMT -5
I might do that next time - see if I can go one size bigger. It just looks so rad having big bombers on there.
By the way, how is a rim measured? Is a 2.15 rim something that measures 2.15 inches across the inside where the tyre bead would contact the rim?
Mick
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Post by hopwheels on Mar 21, 2007 0:36:50 GMT -5
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Post by colinjay on Mar 21, 2007 16:24:45 GMT -5
Hi All,
I found the rim / tire size list. Below is an extract from the list for 1.85 and 2.15 rims;
1.85 RIM
Impirial tyre sizes: 2.75, 3.00, 3.25, 3.50, 3.60, 3.75, 4.10
Metric tyre sizes: 80/90, 90/90, 100/80, 100/90, 100/100
2.15 RIM
Imperial tyre sizes: 3.00, 3.25, 3.50, 3.75, 4.00, 4.10, 4.50, 4.60
Metric tyre sizes: 80/90, 90/90, 100/80, 100/90, 100/100, 110/80, 110/90, 110/100, 120/80, 120/90, 120/100
Mick, You got it! The size of the rim is the internal width between the shoulders of the rim.
CJ
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Post by hopwheels on Mar 21, 2007 22:41:30 GMT -5
So does that mean all of those sizes will work on the rim sizes shown? Or is ther an ideal size? I'd like to go a big or wide a tire as possible.
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Post by brokenicarus on Mar 22, 2007 12:40:48 GMT -5
Cool! those charts are invaluable! So if I can get:
Bridgestone BT45 Rear 110-80-18
Bridgestone BT45 Rear 120-80-18
Bridgestone BT45 Rear 110-90-18
what is the difference? is 110 the distance across the tire and 80 the ratio of width to hight?
hopwheels, where're you ordering your tires from?
This is perfect information, thanks a ton
Davey
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