TC tyres

[Steve Simmons]

Easy enough to remove the rear fenders of a TC. Easy enough to get some wider 19" wheels from Bob G. Those i3 tires will not fit on a stock 2.5" rim, and there is no way they will fit inside the stock rear fenders. But I guess we all know that.

According to Mike, they are smaller than the stock TC tire in both width and height, so they do fit the stock rims as well as inside the rear arches. He's been running them for a while now. They can also be fit by hand! But ignoring all other issues, the size is a deal killer for me. He says he lost an INCH in diameter. That's as bad or maybe worse than those Commander B5 that used to be popular. You'd have to increase your rear end gearing to maintain normal high speed touring. Not a problem for those who just drive around town I suppose.

[Ian R]

Steve,

You seem to have some contact with Mike & I am very interested in using I3 tires.
Does Mike outline what he did for inner tubes ?

Just wanted to add that the BMW I3 uses different tires sizes front/rear.
I presume Mike used 4x BMW I3 front tires ?

[Mark McCombs]

Duncan

Thanks for that helpful information. To add to it, I Had just mounted 4 Bedford brand tires that came from Lucas tire around 10 years ago, kept in a dark ambient environment. They are model A tires 4.75 x 5 by 19. Mounted and inflated they measure exactly 5.0 across the width, and I measure 4.50 width on my fifth Unmounted tire. So it seems that you could figure an additional 1/2 inch from the unmounted measurement to the final mounted and inflated state.

Might come in handy when shopping for tires.

[Duncan M]

I was going by published info on that particular Bridgestone radial. The same info I provided a link for earlier in this thread.
It says the section width is 6.2 inches. As I said early in this thread, the info published by the tire makers is often less than useless. They do usually get pretty close on the overall dia.
If the i3 radial is 27.6 inch dia. that puts it very close to the original original Dunlops.

[Charlie Mac Quarrie]

I've put a set of Bridgestones on my TC to see for myself. I can anticipate the huge improvement with modern tires over 75 year old design as I've gone through this learning curve with my 50s motorcycle, especially in the wet.
Only 2 possible issues are on my radar. Tire wear( which I can't imagine would be worse than the 8 - 10,000 miles I get on the B5s.) and a possible tube issue.
As noted above the tires will reduce my final drive about 5%. I running 4.8 so they will take me back to about 5.1 If I decide to live with the radials I'll buy a new 4.6 set to get me back to my chosen 4.8.
Buying a new crown and pinion would be a small price to pay for the huge improvement I expect from these tires.
I've had 7 or 8 sets of tires on my TC and when I balanced them, each wheel always took 1 to 4 oz of weight. When I balanced the radials no weights were required on any wheel.
Charlie

[Duncan M]

Charlie-
Please post a pic to show how well those 155's fit in back on a stock TC.

[Steve Simmons]

Hi Charlie, no doubt that everything about the tire's performance will be much improved. Modern tires are the single best performance booster our cars have ever seen. I'm sure the wear will also be much better, and the modern tread design will undoubtedly make up for the harder rubber.

Unfortunately the smaller diameter is an insurmountable problem, as no tire manufacturer in their right mind would make a tire like that in a tall profile, since no car maker would ever specify them. I have high hopes for Rob's tires to be a good compromise, but for those like me who love the original look of the B5 too much to change, we're stuck with the old tire tech.

Regarding weight, I never had to use much, if any, weight on the Dunlop B5 through multiple sets. But the new Ensign version of the B5 is a mess. Lots of weights. Otherwise a good tire though.

[Duncan M]

Mark-
I agree those Model A tires should be fine after 10 years of dark and dry storage. They are not radials, after all.

Went for a nearly 100 mile drive today and got the engine and tranny oil heated up to nearly 140F! Diff oil 115F. Outdoor temp was 65F.

A pic from the drive, showing off how well the 30" diameter, 5.2" section width tires fit on a stock TC.

A metric converter will tell us that 155mm = 6.1 inches.

[Steve Simmons]

Steve, You seem to have some contact with Mike & I am very interested in using I3 tires.
Does Mike outline what he did for inner tubes ?
Just wanted to add that the BMW I3 uses different tires sizes front/rear.
I presume Mike used 4x BMW I3 front tires ?

Hi Ian, I asked earlier today for you. He used his original tubes, which are motorcycle tubes. So far no issues. And yes he used fronts, as rears are 20" and would not fit!.

Also in his words... "Been out on my Bridgstone Copia 500, 155/70/19Rs today and still gob-smacked by the ride and the stability."

I also mentioned the Coker radials to which he replied, "The Coker 475/500 19 Rs are a much bigger tyre and would be a very tight fit on the back of most TCs."

[Ian R]

Steve,

Thank you for finding the information.
I’m going to go the I3 front tire route.

I have a 4.55 cwp from my ‘54 Morris Minor sitting on the shelf & I can fit that if the reduced diameter is an issue.
I won’t take my TA on Freeways as it is too darn dangerous so maybe I can cope with the extra rpm.
Have to wait till the weather warms up first…

[Rob Reilly]

4.75/5.00 x 19 tires were on my TA when it came to me. There didn't seem to be any clearance problem.
I wonder, has anybody actually measured the clearance? Or say measured from the center of the tire tread to the side of the body tub?
I measured the width of my American Classic radial with 35 psi pressure and it is 5 inches (127mm); my method was to lay it on the floor and lay a straight edge across it, then measure floor to straight edge.
So from center of tire to body tub you need something more than 2-1/2" (63mm) to allow for body lean, flexing of the leaf springs etc. as we have no transverse links.
My chassis has no body on it and is covered and wrapped up for the winter, so I can't get a measurement of tire-to-chassis right away, but the brake backing plate is outboard of the body.
So it looks like there is enough clearance to me.

IMG_20210320_102129086.jpg (64.32 KiB) Viewed 3989 times

[Duncan M]

That measuring method should be pretty accurate. Thanks Rob. That means the Model A radials would fit in a stock TC. Just barely--section width wise. Also, 30" dia. (Mode A) tires effectively give you a 4.8 rear end ratio when you have the stock 5.125 in place. Around 400 engine rpm reduction at highway speed.

[Rob Reilly]

My crown gear is stamped 8/39 so it is a 4.875 ratio.

Is there anyone that can take a measurement?
body tub inner fender (wing) to center of tire tread?

[Steve Simmons]

That's a great general use ratio on stock tires, and excellent for touring on oversized tires. The Firestone model A tires a lot of people run in our local group give about a 350RPM reduction at highway speed. I'm a stickler for the original tire look, so I have a 4.625 standing by to replace my 4.875. Just have to find time to do the swap.

[Rob Reilly]

It seems to have been the stock ratio for TA.
I just remembered, Clausager's Original T-Series book says the TC body B280 was 4" wider between the rear door pillars than the B270 body of the TA, so perhaps that tire-to-body measurement would not mean anything for me anyway.

[Steve Simmons]

Oh, yes I forgot you had a TA. It was indeed stock. I seem to recall it was the gearbox that had different gearing. The differential housing is almost identical though as I'm sure you know, so the gears are interchangeable. I have TA gears in my TC currently.

[Steve Simmons]

Well, I tried to order a set of American Classic radials but they are completely out of stock everywhere until late Summer. I wanted to give them a try.

Lots of tires are unavailable right now and the second choice, Blockley, wants $450 to ship a set of tires to the USA. Longstone charges around $150 but they don't carry Blockleys, or even a copy of them that isn't either too small or too big.

[Charlie Mac Quarrie]

When going to radial tubeless tires, there is an issue with using tubes in tubeless radial tires. Sidewall flexing, increased heat that leads to tube chaffing and flats.
There is lots of info about this around.
Personally, I have radials on my car to try in the short term. If I decide to keep them on my car, I have a plan to convert my wheels to tubeless.
I won't run my car long term with tubes in the radials.
Charlie

[Ray White]

When going to radial tubeless tires, there is an issue with using tubes in tubeless radial tires. Sidewall flexing, increased heat that leads to tube chaffing and flats.
There is lots of info about this around.
Personally, I have radials on my car to try in the short term. If I decide to keep them on my car, I have a plan to convert my wheels to tubeless.
I won't run my car long term with tubes in the radials.
Charlie

Well said Charlie. My first job was as a tyre fitter (tire fitter) way back when tubeless radials were a fairly new thing. We had great difficulty in explaining to older customers that a tube was not needed,,, but "the customer is always right" was the mantra back then. It was all extra business for us!!!

[Rob Reilly]

There may be some confusion or cross-purpose discussion here.
Are you running with tubes in tubeless radials?
My radials are tube type and the tubes are made for radials.