Maximum tire size on 19” A rims / risks?

[nuwala]

Maximum tire size on 19” A rims

Looking to run bigger tires on my 19" rims as the original 4.75-19 look dis proportional. I’m having hydraulic brakes, so no issue with the brake rods. The speedo and the fender will be adjusted accordingly.

My local tire dealer (Germany) explained, that the 19” A-rims with an width of 3”, can maximum handle a 500/19 tire. That shall be the general rule of thumb: rim width + 2”.
But my dealer did not really have any explanation why. Some tire dealers list the recommended rim width:
6.00-19: recommended rim width 3.50” – 4.50”
6.50-19: recommended rim width 4.00” – 4.50”
7.00-19: recommended rim width 4.50” – 5.00”
7.50-19: recommended rim width 4.50” – 5.00”

What do you think about the risks of having larger tires on the standard 3" rims?
Anyone having experience with 6.50-19, or 7.00-19, or 7.50-19 on the standard 19” rims?


many thanks in advace

[CarlG]

I run 550R19 tires on my stock Model A rims. One guy in our club runs 650R19s on his.

[RichardW]

I have no idea how he did it but I saw this at the Texas TourDSCN5737 B.jpg

DSCN5739 B.jpg

[Redbird]

That is Ron Taylor's car and he is a member of the Lone Star Model A Club in Georgetown, TX.

[updraught]

Our road regulations are mostly downloaded from Europe.

"Recommended" in the US is "Approved" tyre width here, and I believe similar in Europe.
Therefore, the manufacturer approved width for each tyre is supposed to be followed.
I gather that the wall of the tyre is supposed to be straight up and down.

Blockley Tyre on their web site says:

"It is designed to correctly fit rim widths available in period (typically 3 inches for 500 and 2.5 inches for 4.50 sections). Presently the higher performance road cars fitted with, say, a 5.00x19 race tyre have had to be fitted with a rim measuring at least 4 inches across the well as recommended by the manufacturer - A ludicrous situation as cars did not have such wide rims originally. As an example G.P Bugattis, with their aluminium wheels having a width of only 2.7 inches either have to fit these same tyres, or fit non-standard wheels - either solution being unsatisfactory."

http://www.blockleytyre.com/page2.htm


"A friend of mine owns the Zagari photographic archive and by studying the photographs, coupled with checking period data, I think I can safely say that no competition car pre-war had a rim width exceeding 4 inches, which may come as a bit of a surprise to most of us. My just pre-war GP Alfa Romeo only had a 4-inch rim and that was for their widest 7.00 section tyre! I therefore surmised that if one were involved in a big and expensive enough accident an insurer could argue that the Dunlop tyres being used were too large for pre-war rim widths, information which is clearly stipulated in their data. Conversely if wider wheels were fitted to accommodate these inappropriate tyres (as so many have had to do) it could be pointed out that the vehicle has been modified out of specification -and rightly so because wider wheels tend to be built away from the brake drum which is why one often sees them laced on the inside and middle only, widening the track, altering steering geometry and so on and, worst of all in my view, making the cars look like out of character 'hot rods' which we have begun to take as the norm."

http://www.blockleytyre.com/page4.htm

[Henry's Lady's Man]

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I just purchased 550R19 Excelsior Stahl's with tubes. After the powder coating, I guess I'll find out. I don't expect any negative effects.

[Mike Peters]

I used to run a set of oversize 19" tires on our 30 roadster. They were fine except on tight turns.... They would rub the front brake rods. So we went back to 4.75" tires and no more rubbing. Everything is a trade off in life???

[Step-down]

550x19

[updraught]

Just for info:

Excelsior Stahl Sport Radial
$271.00

550R19

• Rim Diameter: 19
• Tread Width: 4.00
• Section Width (Actual): 5.10
• Overall Diameter: 30.10
• Load Index: 88
• Speed Rating: S
• Max Load Capacity: 1235@44PSI
• Recommended Rim Width: 4.00 - 5.00

[H. L. Chauvin]

For those who have reported wider 550-19" tires hitting "one" (1) of their Model A brake rods:

1. Try turning the steering wheel all the way to the "right" and measure distance from tire to the brake rod; and then,

2. Try turning the steering wheel all the way to the "left" and measure distance from tire to the brake rod.

What one finds is that after so many toe-in adjustments over the years, the tie rod is not centered, and it is positioning one of the two (2) front wheels too close to a brake rod and positioning the other wheel farther from the opposite side brake rod.

Re-position tie rod closer to center and everything should work where neither tire contacts a brake rod.

[SeaSlugs]

Originally Posted by H. L. Chauvin

For those who have reported wider 550-19" tires hitting "one" (1) of their Model A brake rods:

1. Try turning the steering wheel all the way to the "right" and measure distance from tire to the brake rod; and then,

2. Try turning the steering wheel all the way to the "left" and measure distance from tire to the brake rod.

What one finds is that after so many toe-in adjustments over the years, the tie rod is not centered, and it is positioning one of the two (2) front wheels too close to a brake rod and positioning the other wheel farther from the opposite side brake rod.

Re-position tie rod closer to center and everything should work where neither tire contacts a brake rod.

Im not doubting you but how would tie rod centering affect things? Wouldnt that have to do with the drag link length and spindle stop "nuts" on the axle itself??

I mean if the wheels are centered and tracking straight and the toe is set correctly how would playing with the tie rod center affect things?

maybe im not understanding something...

[Phil Brown]

I think what is meant is that by centering the tie rod what your really doing is centering the steering box so that it turns the same number of degrees each way

[Y-Blockhead]

Originally Posted by SeaSlugs

Im not doubting you but how would tie rod centering affect things? Wouldnt that have to do with the drag link length and spindle stop "nuts" on the axle itself??

I mean if the wheels are centered and tracking straight and the toe is set correctly how would playing with the tie rod center affect things?

Originally Posted by Phil Brown

I think what is meant is that by centering the tie rod what your really doing is centering the steering box so that it turns the same number of degrees each way

I agree with SeaSlugs. Centering the tie rod does nothing to the steering. The wheels are still going to be pointed in the same direction. The only way to center the steering box is with an adjustable drag link (which Model As don't have). Well I suppose you could bend the steering arm.

We had this same discussion a while back when talking about centering the steering wheel when a shortened pitman arm was installed.

Neat looking tires, Nuala. Are they bias ply or radials?

[nuwala]

Thanks for all comments.
I've found some 6.50 x 19 tires which are specified for 3.0" - 3.5" rims. The tires give a more comfortable feeling than my earlier 4.50 x 19. Somehow a more stable drive without wobble and shaking at higher speeds.

[Beater]

and what brand of tires are those ?