19.5 or 22.5

poorfarmer · 02-19-2011, 07:07 PM

just got back from a 1200 mile round trip, everything went great. new brakes were awesome and 8.13 m.p.g wasn't too bad either. i was wondering if anyone out there has gone from 19.5's to 22.5's? my tires are 7 years old now and since i am going to replace them anyhow was just wondering if it would be worth making the up-grade. plus new alcoas would sure look nice

mikf · 02-19-2011, 07:39 PM

would they fit in the wheel wells? what would you gain?

TrekPR · 02-19-2011, 08:10 PM

22.5's would mess with all the gear ratios and I doubt you could find the bolt pattern. Alcoa makes wheels for the 19.5's but the studs have to be changed because the aluminum wheels are thicker which requires a longer stud both front and rear if you want the hub covers to go on. The rear studs can be used on the front if they are not buggered taking them out. The studs run in excess of $20 each. The Alcoa's are around $1700, been there done that.

poorfarmer · 02-20-2011, 09:40 AM

thanks mr trek, at this point just checking into it.

Mutha · 02-20-2011, 10:53 AM

I have a 2004 Safari TREK W-20 that was changed from 19.5 to 22.5 using ALCOAs. The wheel wells are all the same on any manufacturers GASOLINE coaches. The studs, FRONT and REAR DO NOT have to be changed out. All Workhorse "W" (20, 21,22 & 24) use the same 8 lug pattern wheels and common lug nuts.

You do have to purchase 2ea. 22.5 STEEL Wheels for the rear inside duels and 4ea, of the ALCOA Aluminum wheels at a total cost of $2200 (approx) and 6ea. new 22.5 tires at $2000 (approx).

I have a 4:88 rear axle ratio and had to have BRAZEL's RV re-program my ECM to correct my 10% speedo error and change the ABS setting to 22.5 from 19.5.

My fuel mileage went up about 1.5 miles per gallon to and average of 8.5 and my ride and handling improved to "SPORTS CAR" status. I have NO chassis add-ons whatsoever.

If you decide to make the change I will be happy to email or phone you with all the supplers (and cost) I dealt with to make my change over. You are welcome to email me at "glenn AT oem-engineering DOT com".

good luck - Glenn

Midniteoyl · 02-20-2011, 02:06 PM

What actual size tires did you switch from/to? I'm having a hard time finding tires that arent way off in diameter...

Mutha · 02-20-2011, 03:25 PM

Quote:

Originally Posted by Midniteoyl

What actual size tires did you switch from/to? I'm having a hard time finding tires that arent way off in diameter...

Jim, my rig came from Workhorse with Michelin XRV 245/70R 19.5F and I replaced them with What Workhorse uses on their chassis with 22.5 wheels, which is Michelin XRV 235/80R 22.5G.

Glenn

DriVer · 02-20-2011, 04:54 PM

Quote:

Originally Posted by Mutha

I replaced them with What Workhorse uses on their chassis with 22.5 wheels, which is Michelin XRV 235/80R 22.5G.

Good choice. √

FDchief · 02-20-2011, 05:03 PM

Quote:

Originally Posted by TrekPR

22.5's would mess with all the gear ratios and I doubt you could find the bolt pattern. Alcoa makes wheels for the 19.5's but the studs have to be changed because the aluminum wheels are thicker which requires a longer stud both front and rear if you want the hub covers to go on. The rear studs can be used on the front if they are not buggered taking them out. The studs run in excess of $20 each. The Alcoa's are around $1700, been there done that.

Not true on the studs. I replaced my steels with Alcoas in '03 when the coach was new. They are a special pattern and offset though. I love mine.

TrekPR · 02-20-2011, 05:23 PM

Chief,

I don't know if the caps or the studs aren't the same but I assure you it is true that my studs had to be replaced. When I went to pick the rig up the caps were not on because the studs weren't long enough, I hit the roof because it was a 90 mile drive back home and a 3 day wait to make the drive again. Let's just say it isn't true for your rig.

TrekPR · 02-20-2011, 05:26 PM

Glen,

That is quite a modification. I had no idea it would even be possible, only a Treke.

max49 · 02-20-2011, 07:20 PM

Wow Glen, I did'nt think you could just swap 19.5 tires for 22.5s either. Since you had your speedometer corrected from the app. 10% error, does that mean your final drive ratio is 10 % higher now? If so I would assume @ 60 mph in high gear, you're only running around 1950 RPM?
I would like to have 22.5 tires but I would buy a new rig and never consider gearing my present MH that high. My engine would never be able pull that tall gearing. Mine already does 80 MPH at 2900 RPM in high gear on a flat road with no wind.
Mine's has the GM 4 speed but it's hard for me to imagine that the Allison final drive ratio is much different.

Mutha · 02-20-2011, 08:08 PM

Max, I have the Allison 5 speed.

The difference in TIRE diameter is 3.8" (19.5 dia=33.3" vs. 22.5 dia=37.1"). If you divide 3.8" by 33.3" you get .114, which is 11.4% (instead of my rounded off 10% in my original post). When my speedometer was showing 60 MPH, I was actually going 68.4 MPH or every time my drive shaft in 4th gear (1:1) turned 4.88 revolutions my 22.5 wheels & tires moved me 18.1" farther along than the 19.5 wheels and tires -- hence the increase in fuel mileage. If I am in flat/rolling hills I run with the overdrive turned on (5th gear .07:1) and about 1850 RPMs (60 MPH) without ever shifting out of OD. If I am in Hills/Mountains I turn the OD off and run in 4th gear (1:1) and about 2200 RPMs (60 MPH). Also the higher load range on the tires allows me to run lower air pressure (better ride) and UNOFFICIALLY increases my GVWR to 22000. My last CAT Scales GVW (fully loaded) about 3 months ago was 19983 LBS, so I am below my OFFICIAL 20,700 GVWR.

Regards - Glenn