Tire Size and Speedometer

[Jetcab]

I just bought new tires for my 2001 PT Limited Edition.
Michelin MXV4 PLUS XSE All season performance 215/55HR16 93H.
(It came with 205/55HR16)
The car handles better, however the speed now does a funny movement now, when I speed up the speedometer arm goes to what seems the proper speed read out, then when I slow down the speedometer drops dramtically down. I was told as long as I didn't change the height of the tire I wouldn't have any issues with the speedometer. Is that's what going on...the tires are 215 rather than 205's...?

Thank you for your help.
Jetcab

[gonzomania]

Try this site:http://www.1010tires.com/tech.asp . Then you can determine what's happening

[tom-t-rifik]

You've got to change the aspect ratio when you change the tire width or the height of the tire will change, too. Check out www.tirerack.com for plus sizing tips. They suggest a 225/50-16 as a good option. When you changed the original 205/55-16's to 215/55-16 you increased the width, but left the aspect ratio the same, which made the tires slightly larger (taller) which screwed up your speedo. The computer's trying to compensate, but can't.

[CREWZIN]

JetCab,

Here's a site that gives you the exact differences between two tire sizes. Fill the blanks and hit "compare".

http://www.1010tires.com/TireSizeCal...?action=submit

[quicksilverdon]

Everybody answered you, but I want to add...
WELCOME to the Forums.

[SteelBlueGT]

Yes! Welcome to cruiser links! I don't think your speedo problem is with your tires. I think accuracy is the only danger in changing tire size not what you report when you slow down. I know a slew of people that did exactly what you did and no speedo malfunctions. Yes their speedo is not as accurate but that did not bother them at all.

If you go to Tire Rack and compare your stock tire RPM (Revolutions Per Mile) with what you boght you can tell just how far off your speedo should be. You can get a malfunctioning digital speedo by buying tires and or wheels that are out of its range but yours are not like that at all. In fact the only possible malfunctioning problem I am aware of is the anti lock brakes and low speed traction control equipment which you probably don't have on your model and year Cruiser.

[Jetcab]

Thank you for the warm welcome and the excellent technical replies to my quesiton. Based on the research and inputs I returned the 215's and had them replaced with the original size of 205/55/16. The speedometer likes it there haven't been any unusally drops from the speedometer needle.

Now, I have another issue, that has surfaced recently. When I apply my brakes and the speed is slowed to approximately 10mph give or take, the car acts like it's stalling and drops it's speed dramatically and I feel a sudden jerk I can't tell whether the car jerks forwards or backwards. I feel a sudden jolt as if everything shut down at once. This happens intermitently and typically if the car is cold or when I first turn on the air conditioner.

Any thoughts?

Thank you,
Jetcab
2001 LE

[AlmondTurbo]

Jetcab, I replaced my stock 205x55x16 Goodyears LS with Yokohama AVID H4s 205x60x16. The new tires are 7/8 inch taller than stock (clear the front struts by 3/16 inch)(no cable chains). My speedometer seemed to be reading 5% fast with stock tires. It is now dead accurate at 67 mph (checked by radar). The movement of the speedometer needle was never effected by the tire size change.

[Jimbo]

you can try this site
http://www.dakota-truck.net/TIRECALC/tirecalc.html
Also like to add welcome to this forum,sorry I can't
help you with your other problem.You might want to repost
under new heading.Again welcome and good luck