How much difference does tire size make.

[Gauche1968]

So I have been noticing some marked differences in the driveability of my 3 vans as of late. The 84 Westy, which has the stock tire size seems to be able to maintain power and speed in higher gears more readily than the 84 GL. A hill that the westy will take in 3rd gear at ease, the GL seems to want 2nd. The Westy also seems to ride out turns in 2nd much easier, whereas the GL seems to want 1st gear coming out of turns at times. The Westy is running the stock tire size, whereas the GL has the 195 RA08s. Could these differences be caused by the difference in tire size or is there something more sinister going on with the GL?
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1984 Vanagon GL
1984 Vanagon Westy

[PDXWesty]

I noticed a big difference in power and speed on my westy when I went from stock tires to 27x8.5x14. Big difference....
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89 Westy 2.1 Auto

[seanjenn]

I've got 195R14 RAO8s on mine and they are awesome, van has no power issues with them. Corners in second and all the hills in third no problem.
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1987 GL Sunroof
2.1 4 spd

[jacob.]

I've got stock 14" steel rims with some kind of 195 r14 tires on there. Turns in second, hills in 3rd feels good. Just like the above poster.

<edit> I guess you've got a point pdxwesty, I have nothing to compare how my tires feel with.
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[PDXWesty]

If you haven't changed tire size, you really don't know how the van feels with different sizes. You can put on 185's and switch to 27" and you will notice a difference. If all you've ever driven on is one size with your van, there's no real basis for comparison. The OP was asking for comparisons.
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89 Westy 2.1 Auto

[AtlasShrugged]

I had the stock sized tires on 14 inch factory alloys and switched to the 195 RA08s.

With an automatic transmission, I did not detect any real performance issues with shifting or power. My speedometer is more accurate now though.
Highway engine speed (RPM) is slightly more relaxed too.

[Westy-Life]

When you have some time to kill try switching the wheels from each van and redo your test.

Dave
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86 Westfalia with 03' TDI Auto trans

[MarkWard]

Taller tires are a poor mans gear change. I would expect a taller tire to lug the engine going up an incline where a shorter tire would not. Is that what you are experiencing? The answer to your question is yes, tire diameter has a direct affect on engine operating rpms. From memory going from stock tires on my conversion to 215/65/16s lowered rpm 300 at 70mph. With the TDI conversions, we are trying to get the working rpms lower since max torque is around 2000 rpm.

[hiram6]

Yep, my highly sensitive butt dyno impressions tell me that when I moved up to larger 15 inch 75 series BFG A/Ts from the stock 14 inch 70 series, I had noticeably less "escape speed" from a start, and less power when climbing hills. Have to downshift much more often. Trade-off is I have lower rpms at freeway speeds.
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1985 Westy, 1.9L automatic (Daisy)
1996 Mazda Miata
1998 Jeep Grand Cherokee 5.9 Limited

You can't lie around on the beach and drink rum all day.................unless you start first thing in the morning.

[PDXWesty]

[funagon]

This was my opinion:

http://www.thesamba.com/vw/forum/viewtopic.php?t=242032&start=20

"For me, the loss in performance is serious enough that I don't recommend a larger diameter tire for a stock vanagon . . . Changing to a larger diameter tire has made my van into a slow steering, poor handling, slow vanagon."
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1990 GL 7-passenger
2.2 liter WBX