Tire sizes and/or conversion?

[The Seeker]

Anyone know about tires sizing and how tire sizes can be converted?

Specifically, I am attempting to find out if a tire marked " 110/90 - 19 " is the same size as a " 4.10 - 19 ".

 

[ducarly]

Hi Seeker:
If you pay me the ticket and food, make you care 24 hours!! Ja, Ja! :y24: :y24: :y24:
A tire 110/90 x 18" is 110 mm in width, 90% of the width (99 mm) high and 18 "rim, and that is equivalent to 4.00 x 18", a tire from 4 "tall and 18" rim.
Good routes, Carlos (yet again!) From Ensenada, Argentina.

 

[ducarly]

Hi Seeker:

How to read a cover measures? Example: 130/70-17 58V
http://www.myphotos.yahoo.com/s/210zwun2mgqpir04f3d4#slc2cXwGZF.thgheArk4ZYkKZmxonxjZq
130 cross-section width in millimeters (S)

70 Ratio of the top of the cover (from the basket on the floor) by its width, expressed as a percentage (H ÷ S)

17Diametro ring, in inches (Ø)

58 Load Index

V Speed Rating

The load index, represented by a two-digit code indicates the maximum load that the cover can be operated to be safe.

The speed rating (RANK), represented by one or two letters on the side of the cover, indicates the maximum speed at which the deck can be operated under safe conditions when properly loaded and inflated.

Code mph km / h
B: 31 50
Q: 100 160
V:> 130> 210
J: 62 100
R: 106 170
ZR: 149 to 168 240 to 270
L: 75 120
S: 112 180
W: 168 270
M: 81 130
T: 118 190
(W):> 168> 270
P: 94 150
H: 130 210
Good Road, Carlos from Ensenada, Argentina

 

[The Seeker]

So a 110/90 tires is equal to a 4.00 tire?

It looks like my new (to me) Bonneville has too narrow of tires on it!

 

[Rocky]

Considering his experience, Grandpaul is probably the best person to answer this question.
I have never fitted metric tires to either of my old bikes. I prefer the correct size and tread for the vintage look. Compared to my modern bikes those small old style tires look like large bicycle tires. As small as they may be, with modern tire compounds, the old style tires stick very well. But I don't ride the old bikes hard so don't need modern metric rubber to stay on the road.
There are any number of tire comparison charts on the internet and a 110/90 seems to be the one to replace a 4:00 tire. But you have to be careful with modern tires due to clearance problems with the forks and swingarm.
Choose carefully.

 

[ducarly]

Hi Seeker:
4.00 (4&quot is 108 m.m. (1"= 25,4 m.m.). Good Road, Carlos from Ensenada, Argentina. :y115:

 

[The Seeker]

What I am attempting to ascertain is if the tires I presently have on this '78 Bonneville are the correct size or not.

I know for sure the rear is too narrow since it's a 4.00 - 18 and the bike should have a 4.25 - 18.

On the front, it has a 110/90 - 19 and the bike should have a 4.10 - 19.

So if a 110/90 is equal to a 4.00, then the front tire is also too narrow.

What is weird is that the tires are a matched set of Continentals of the same design and model...except that one is metric and the other is standard.???

 

[Rocky]

According to the John Nelson book "Bonnie" the T120 and T140 were both fitted with the same wheels and tires all through the 1970's. The book also gives the US variations in specs and the wheels and tires were not changed.

F - 3.25 x 19
R - 4.00 x 18

For what it's worth.

 

[CarlS]

AJ, those tires were narrow, especially by today's standards.

 

[The Seeker]

[quote author=Rocky link=topic=10464.msg51407#msg51407 date=1285925390]
According to the John Nelson book "Bonnie" the T120 and T140 were both fitted with the same wheels and tires all through the 1970's. The book also gives the US variations in specs and the wheels and tires were not changed.

F - 3.25 x 19
R - 4.00 x 18

For what it's worth.
[/quote]

Hmmmm???

The workshop manual that Carlos gave the links to says 4.10 - 19 and 4.25 - 18 ???

My '69 Tiger has a 4.25 Dunlop on the rear as well.

 

[Rocky]

I'm certainly no expert on this subject, but 4.10 seems like an awfully large tire for the front.
I've never heard of anything but a 3.25 for a front tire - but then I haven't heard everything.
My '70 Triumph calls for a 3.25 x 18 front tire. There were no tires available in this size so I fitted a 3.50 x 18 and you can certainly tell it's large.
My BSA 441 also has the same size tire and I tried a 3.50, but it rubbed hard on the fender so I had to use a 3.00. The bike runs and handles just fine.
I have a modest library of reference material. Tell me again the year and model of your bike and I'll dig around some more when a have a few minutes.

 

[ducarly]

Hi Seeker:
I do not know why, but 4.10 is smaller than 4.00, equal to 3.50 - 3.60 or so.
My TR6R takes 3.25 - 19, although I fit 3.25 - 18 (it is more maneuverable at slow) and 120/90 - 18 in rear (it goes as wide as measured from the swingarm to the chain).
Good Roads, Carlos from Ensenada, Argentina

 

[Rocky]

More beef for the broth :ya2:
Using the 1985 Roy Bacon book "Triumph Twin Restoration" as my guide, a 3.25 x 18 or 19 front tire was used about 95%+ of the time on all Triumphs. In a couple of cases for certain models a 3.50 x 19 was specified as was a 3.00 x 19 and 20, and a 3.25 x 17.
Other than a couple of oddball cases way back a 4.00 x 18 was used on the rear. A 3.50 x 19 was used back in 1954.
The stats only cover 1946 to 1972.
A tire conversion chart is also shown as follows:

Original Low profile Metric
3.00 3.60 90/90
3.25 3.60 90/90
3.50 4.10 100/90
4.00 4.25/85 110/90

I think the low profile tire is where the numbers start to get fuzzy and confuse things.

Once again, for what it's worth :wink:

 

[The Seeker]

So what I presently have is the equivalent of a 4.10 - 19 in the front and a 4.00 - 18 in the rear. Maybe that's why the bike feels a little unstable at high speeds?

 

[CarlS]

That could certainly do it.

 

[The Seeker]

I really think I have gotten spoiled after riding my Trophy with the full fairing, windscreen, and all the weight too. After riding the '78 Bonneville recently and then switching back to the '96 Trophy to meet Joe for dinner the other night, I was astounded by the difference. The wind on the Bonneville feels like it's going to pull my head off my shoulders. Maybe a new aero-style helmet would help, but I never needed one with the Trophy. And even though the Bonneville had disc brakes, they are nothing compared to the modern disc brakes of the Trophy.

 

[Rocky]

As you have discovered, The difference between then and now is almost like night and day. It isn't for everyone.
I was out on my H***a today which is a fuel injected water cooled four cylinder. I call it my "H***a Civic" :ya2:
Comparing this to one of my old bikes is no comparison at all. But I love riding the old bikes because that's what they are - a throw back and nostalgic riding. As rough and crude as they may be compared to modern machinery, they're very reliable and perform very well within their limits - and just plain fun.

 

[The Seeker]

I think I've decided upon going with getting Dunlop K70s front and rear with a 3.50 front and 4.10 rear.

 

[Rocky]

That's what I use on both of my old bikes and they perform very well.

 

[The Seeker]

Each of those are one step up from the width size specified for the bike, but as long as they'll fit (which they will) I like to get as much rubber footprint down on the road as possible. I'm still keeping the proper ratio though between front and rear.