ramifications of adding a spacer to dual wheels

Hi,

The first results and impressions:

speedometer error is 8% so at 80 kph reading I am going 85 kph

I found the biggest hill in the area and was able to maintain my usual cruising speed of 80 kph. The tranny downshifted twice. It did the same with the "stock" tires.

1800 rpm = 80 kph (according to gps device) on the OEM tires that was 76 kph.

scan gauge reads 46 mph @ 1800 rpm--confirming the 8% error

Initial trip was with a head wind/side wind. Mileage appears to be measurably improved--but that won't be known for sure until I have a few thousand kilometers "on the clock"

No difference in engine temperature with the larger wheels/tires

It did take about 30 minutes of driving for me to get "used to" the new configuration.

I was on a four lane highway and had no opportunity to see how trucks going the other direction might affect the ride.

At one point there was a gusting wind situation. No extra sway seemed to be evident.

Road noise is reduced--but there is a low pitched rumble that was not there before. It got better (or perhaps I became desensitized to it) as the trip progressed (Regina to Saskatoon, destination Pike Lake, SK)

There was fairly vicious thunderstorm at the Black Strap Valley. I would normally have dropped out of cruise--but decided to risk leaving it on. There was no issue of hydroplaning nor loss of stability.

Ride is somewhat smoother.

I can tell the difference in height--which surprised me a bit.

I hope to find a washboard road tomorrow.

I did "take it up" to 110 kph to pass a slightly slower moving vehicle. I found I was over correcting on the steering at the higher speed.

So far I'm pleased with the results.

I can hardly wait to confirm the increase in miles per gallon. I should know for sure by about July 6th.

I think that their statement of a failure may mean failure to stop in time due to increased stopping distances due to mass increase, not a catostrophic explosion of the brake system. I'm sure their lawyers were involved also.

I'd be sure to check with the vehicle or rear axle asembly maker to make sure that the w;heel bearings are not overloaded due to the additional moment arm of the verticle load.

will the van body of the class C clear the bigger tires. i know the older gm doesnt very well. I would check into that before spending a bunch of money.

Hi Tom,

I'll be changing all the tires not just the rear ones.

Tom_Anderson wrote:

mena661 wrote:
How do you get a brake failure from changing the size of tires?

You probably won't. But a difference in size between the front and rear tires can
"confuse" 4-wheel ABS systems that read that information as rear wheels that are turning slower than the front (possible skidding condition). That may trigger the warning light.

Another thing to check is the spacing between the inside dual and the springs/spring clamps. On my E350, the stock wheels/tires on the inside dual clear the spring clamp by a 1/2 inch at best. Changing to a larger offset on the inner may not clear.

mena661 wrote:
How do you get a brake failure from changing the size of tires?

You probably won't. But a difference in size between the front and rear tires can
"confuse" 4-wheel ABS systems that read that information as rear wheels that are turning slower than the front (possible skidding condition). That may trigger the warning light.

How do you get a brake failure from changing the size of tires?

The tire size change software on 1010tires.com flashes a possible brake failure warning message when the new tires are more than 3% larger than the existing ones. Your planned swap is a 8.33% difference. Why do you want to change them? It will also affect your MPG and your speedo reading.

Hi,

You folks are wealth of information. Now when I do talk to the tire folks I'll have some idea of what they are suggesting to me!

Thanks to all of you.