Tire size revisited

[64beam]

Hi,

Sorry to re-visit this topic again, but after reading a number of previous threads regarding the original Alpine tyre size I am still a little confused. I have had a look in the WSM 124 which states a radius of 11.25in to 11.50in depending upon the tyre or WSM 145 states a radius of 11.41in to 11.64in depending upon the tyre. From what I can gather, I believe the original tyres would have been around a 75 to 80 profile based on a 155 or 165 width. So using one of the online tyre calculators, a 185 width tyre should be a 65 or 70 profile to keep the speedo within about 1-2%. The reason I am asking is that I think my tyre profile is too high at 185/75R13. Could someone please confirm this?

Thanks, Robin.

 

[Barry]

Robin,

Compared to the original tires, the closest modern equivalent is a 155/80-13 which is about 914 revolutions / mile.

185/75-13 = about 870 revolutions / mile

185/70-13 = about 897 revolutions / mile

185/65-13 = about 926 revolutions / mile

Even if you exactly matched the revolutions / mile of the original tires, I would be very surprised if the Alpine speedometer was accurate within +/- 1%.

If you are using stock width wheels, most tire fitment guides indicate that a 185 section width radial is too wide.

Your car, your choices.

 

[atallamcs]

Tires

I have 185 x 70 x13 on my Harrington. They look right and the overall diameter is right.
Bill

 

[Jim in PA]

Tire size

Last year I replaced my C78- 13" Bias Ply SEARS tires because they were 26 years old. Still lots of meat on the tread but dangerously old and not to be trusted. My spedo was not accurate at all with those tires. When running through a Radar Speed Limit sign I had 25 mph on the speedo but 31mph on the radar sign.
With my new 175- 70R13 I got nearly the same speed on the speedo as on the radar sign. I know the Alpine speedo isn't the most accurate thing and the radar sign must have a +/- too but the two were, and still are, very close each time I get the chance to compare. I make several passes through the Radar speed signs when I find them and my speedo seems to be close enough at 25, 35, 40, 55 and 65 mph that I have no worries.
When I was looking to replace my tires I was going with the thought of 155 or 165 size being close to the original 560 or 600x13. Both 155 and 165 radials looked like toys! They didn't look right. Too narrow and too little tread width even if it is the closest size to original rubber. (My car is not the concourse original type of vehicle)
I had 175 and 185 tires brought out and the 175's seemed to be the best looking as not being too small but not too large either. The 185-70x13 looked like they were a bit too wide for the 4.5" stock width wheel on my SV but they will work fine as many people will tell you. The 175 size didn't push the limit of the wheel width. The 175's were the best looking profile, width and height and still be within the limits of what the wheel and the car itself would tolerate.
So far after 2000 miles, the 175-70x 13 radials have been great. I can't get them to squeal in the turns...and I've tried! My only regret is not buying the narrow white wall tires. I think they look best when using the original caps and trim rings. My blackwall tires will have to do for now...
Jim

 

[64beam]

Hi,

Thank you for the replies. That confirms that my tyres are one profile too big, meaning that my speedo will be showing approximately 3 mph slower at 60 mph. I also have aftermarket rims so the 185 width will not be an issue.

Regards, Robin.

 

[alpine_64]

Hi,

Thank you for the replies. That confirms that my tyres are one profile too big, meaning that my speedo will be showing approximately 3 mph slower at 60 mph. I also have aftermarket rims so the 185 width will not be an issue.

Regards, Robin.

Rob,

If this is in regards to your new tyres on the Tuger.. you have to take into account that the Tigers speedos were not accurate because of the gears that ford had for the trans.. also depends which gear is in your car if it was replaced.. i cant remember which colours indicated which drive gears.. but its on the net and i think might even be in the SS catalogue

 

[64beam]

Rob,

If this is in regards to your new tyres on the Tuger.. you have to take into account that the Tigers speedos were not accurate because of the gears that ford had for the trans.. also depends which gear is in your car if it was replaced.. i cant remember which colours indicated which drive gears.. but its on the net and i think might even be in the SS catalogue

Hi Michael,

Happy new year by the way . No this is not the Tiger, I am refering to the Alpine. It needs the rear tyres replaced with something decent. I have it at home to do some maintenance on it (brake & clutch fluid change, grease and a few other little things). I will give it a run on the next Escape outing.

Regards, Robin.

 

[alpine_64]

Hi Michael,

Happy new year by the way . No this is not the Tiger, I am refering to the Alpine. It needs the rear tyres replaced with something decent. I have it at home to do some maintenance on it (brake & clutch fluid change, grease and a few other little things). I will give it a run on the next Escape outing.

Regards, Robin.

Happy new year rob.. i have ben under the alpien the last few days.. sump is off and clean.. also for those interested.. the alpine SI/II oil pump uses 5/16 bolts to locate it.. the 1725 pumps use 1/4.. and the landings the holes go through are much smaller on the 1725 pump.. so drilling them out. .be careful.. hopefuilly the alpine will hit the road again this week... maybei can escape run it too

 

[64beam]

Happy new year rob.. i have ben under the alpien the last few days.. sump is off and clean.. also for those interested.. the alpine SI/II oil pump uses 5/16 bolts to locate it.. the 1725 pumps use 1/4.. and the landings the holes go through are much smaller on the 1725 pump.. so drilling them out. .be careful.. hopefuilly the alpine will hit the road again this week... maybei can escape run it too

Did the pump fail or are you just going for higher oil flow? Is that the final upgrade on your Alpine? I also had to change the battery on the Alpine as it finally failed. I haven't had any trouble with the overdrive when I have been driving it over the last two days either. I'm waiting for it to slip again.

Regards, Robin.

 

[alpine_64]

Did the pump fail or are you just going for higher oil flow? Is that the final upgrade on your Alpine? .

The pump hadnt failed -yet - it was slow to build up pressure.. i was plannig to upgrade to a 1725 pump long ago.. when the gearbox lost a tooth in May 2007 i figured id do that at the same time.. well between rebuilding the new OD box, pulling/reinstralling engine and transmission it was march 2009 before the car was on the road again.. and of course.. i had frgotten to do the pump while the motor was out.. took it for a drive.. then remembered

Anwya.. between having motivation and time.. its back to end/start of year hoplidays before i have got at it.. so fingers crossed its all good after this is done..

as for final mods... no.. there is still1 more alpine engine to build.. theone in the car is the SI motor i have always had (rebuilt twice over and then some changes)

the new motor will be 1725 based.. im almost finshing collecting parts.. i now just need more money and time.. anyone got any of that NOS?