Tyre choice advice

I have just fitted Bridgestone BT45 3.50 18 to the front of my 750GT and it is fouling on the shoulder. This is a rebuild so the tyre it replaced was a 30 year old Metzler. In theory the 3.50 is equivalent to a 90/100 18 so was thinking of replacing again with a BT46 90/90 18. Measures the 3.50 fitted on the wheel at it measure 102mm wide (4.00) with a side wall from bead of about 3.50.

Anyone had this problem or can measure the actual width of a tyre fitted. Have tried adjusting the mudguard (original) but cannot get it to clear, but it only just rubs.

Thanks
 
2Types said:
I have just fitted Bridgestone BT45 3.50 18 to the front of my 750GT and it is fouling on the shoulder. This is a rebuild so the tyre it replaced was a 30 year old Metzler. In theory the 3.50 is equivalent to a 90/100 18 so was thinking of replacing again with a BT46 90/90 18. Measures the 3.50 fitted on the wheel at it measure 102mm wide (4.00) with a side wall from bead of about 3.50.

Anyone had this problem or can measure the actual width of a tyre fitted. Have tried adjusting the mudguard (original) but cannot get it to clear, but it only just rubs.

Thanks
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They do run really close, it’s very difficult to workout fitted width with modern tiyres as it depends on the rim and how they are labelled on the tyre. I loosened all the mudguard fittingsand rocked the whole thing around to find the sweet spot and it only just clears. Mines 100/90 Pro Max - I found it quite difficult to find a matching pair in these old fashioned sizes. The original Pirelli ribbed cleared by a country mile.
 
BT45 in my experience are pretty much true to size. My well used front 100/90x18 on OE Borrani rim measures 98.5mm wide. Seems odd that your 3.5" tyre measures 102mm when it should be just under 90mm as you say. Presumably your rim is original?
 
Rob said:
BT45 in my experience are pretty much true to size. My well used front 100/90x18 on OE Borrani rim measures 98.5mm wide. Seems odd that your 3.5" tyre measures 102mm when it should be just under 90mm as you say. Presumably your rim is original?
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Everything is original.

Had another fettling session with the mudguard and have about 4mm clearance so Hooe it will stay that way. Time will tell!
 
100 profile tyre is going to be taller than a 90 profile tyre, so theres your problem. 100/90-18 is a common size tyre for modern triumph bonnies, if it gives you trouble go with a 90 profile.
 
2Types said:
Had another fettling session with the mudguard and have about 4mm clearance so Hooe it will stay that way. Time will tell!
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Is that 4mm clearance at the side of the tyre, or radial clearance between the tyre and mudguard?

A tyre will change its aspect ratio at speed. The diameter will "grow" a small amount due to centrifugal force. I dunno how much in mm or % that growth would be (probably depends on speed rating) but it's possible that 4mm is insufficient radial clearance at the centre of the tread.
 
They foul next to the mudguard brackets by the speedo cable, GTs have slightly less clearance on this side than the brake side. Any growth with speed should actually help if anything. I contacted four other owners of standard GTs and all the front Wheels are not exactly central to the forks .
 
sideshow said:
And battery 😂😂😂😂
But I do feel sometimes it’s hard to know what to use be it oil , battery or tires. I ask these questions too , so I don’t go down the wrong route!
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And what about lead free petrol? Do you use additives, octane boosters, fuel stabilisers? What do you think of ethanol in the fuel?

Do you ride your bike?

Paul
 
Paul Marx said:
And what about lead free petrol? Do you use additives, octane boosters, fuel stabilisers? What do you think of ethanol in the fuel?

Do you ride your bike?

Paul
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I do. More than most. The ones that are road legal (5 of 10) are daily riders
 
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Paul Marx said:
And what about lead free petrol? Do you use additives, octane boosters, fuel stabilisers? What do you think of ethanol in the fuel?

Do you ride your bike?

Paul
Click to expand...
Hi Paul,
my pal who runs a guzzi lemans mk1 and a ducati 900ss has done a fair bit of research on comparing modern fuels and it seems that Esso supreme unleaded 99ron does not contain any ethanol, despite it being labelled as E5.
my SF0 did seem to run noticeably nicer with this in the tank, and I didn’t drain the float bowls after my last ride in late November, I will inspect them for the dreaded corrosion before my next ride come warmer weather.
marty.
 
Starman said:
Hi Paul,
my pal who runs a guzzi lemans mk1 and a ducati 900ss has done a fair bit of research on comparing modern fuels and it seems that Esso supreme unleaded 99ron does not contain any ethanol, despite it being labelled as E5.
my SF0 did seem to run noticeably nicer with this in the tank, and I didn’t drain the float bowls after my last ride in late November, I will inspect them for the dreaded corrosion before my next ride come warmer weather.
marty.
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I live in France.
There's alcohol everywhere.

I never drain the float bowls on any of my 750s.

Paul
 
Paul Marx said:
I live in France.
There's alcohol everywhere.
Click to expand...
especially in the French?
i love France, my pal with the guzzi and Ducati has a place there, many,many happy memories of riding some magnificent roads, fabulous food and wines, and with far less traffic than in the UK. It was heaven!
Paul Marx said:
I never drain the float bowls on any of my 750s.

Paul
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Is your local climate mild in winter?
iirc,isn’t it the water that gets absorbed by the ethanol from air in the storage tanks, fuel tank and float bowls comes out of solution in freezing weather, then sits at the bottom of the tank and float bowls, hence the corrosion?
( anyone who is knowledgeable on this phenomenon please jump in here and correct me if I’m way off)

and Paul, please share details of your 750’s?
my 1972 SF0 is my first laverda, I have other bikes, but I wish I had owned an SF long ago,( funds / availability never seemed to coincide!) I am really enjoying riding and tweaking it, the more I ride it, the more I love it! it is one of 3 bikes I will never, ever sell.
marty.
 
Starman said:
especially in the French?
i love France, my pal with the guzzi and Ducati has a place there, many,many happy memories of riding some magnificent roads, fabulous food and wines, and with far less traffic than in the UK. It was heaven!

Is your local climate mild in winter?
iirc,isn’t it the water that gets absorbed by the ethanol from air in the storage tanks, fuel tank and float bowls comes out of solution in freezing weather, then sits at the bottom of the tank and float bowls, hence the corrosion?
( anyone who is knowledgeable on this phenomenon please jump in here and correct me if I’m way off)

and Paul, please share details of your 750’s?
my 1972 SF0 is my first laverda, I have other bikes, but I wish I had owned an SF long ago,( funds / availability never seemed to coincide!) I am really enjoying riding and tweaking it, the more I ride it, the more I love it! it is one of 3 bikes I will never, ever sell.
marty.
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My climate in Northern France must be identical to what you have in South Wales. I'm nearer London than you are.

I have 3 750s running: 1970 S, 1973 SF2, 1976 SFC. And three non running, 1969 650 and 1969 GT, 72 ish ex works ish racer.

Paul
 
what are great collection, and an SFC! you are a lucky man indeed! Aren’t the 650’s quite rare? Like only 50 or so made?

as for climate, s wales has a reputation for having a wet micro-climate, cardiff supposedly having the highest rainfall of all uk cities, with rain every day.
this is actually not true, I distinctly remember a date in july 1978 when we had only two light showers, the first was 7 am till 12,noon, then 2pm till midnight…
it became a national holiday…
 
Exmoor beast said:
They foul next to the mudguard brackets by the speedo cable, GTs have slightly less clearance on this side than the brake side. Any growth with speed should actually help if anything. I contacted four other owners of standard GTs and all the front Wheels are not exactly central to the forks .
Click to expand...
That's really helpful I was concerned as it did not seem quite central.
 
Lee87H said:
I have been running Bridgestone Spitfire s11 100/90 - 120/90 on my 3C ,work very well, of course I'm not grinding pegs or anything like that, I save that riding for my modern sportbike.
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I like the look and sound of these Spitfire s11s for a few of my bikes. It seems they are designed as tubeless tyres: is there an issue with running a tubeless tyre (with tube of course) on a Lav or other rim not specifically designed for tubeless tyres? I vaguely recall some discussion though can't find it..
Thanks.
 
O
AndyW said:
I like the look and sound of these Spitfire s11s for a few of my bikes. It seems they are designed as tubeless tyres: is there an issue with running a tubeless tyre (with tube of course) on a Lav or other rim not specifically designed for tubeless tyres? I vaguely recall some discussion though can't find it..
Thanks.
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Your ok fitting a tube in a tubeless cross ply - not really supposed to fit them to a radial.
 
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