Prs & C7 Suspensions - Snowmobile World : Your #1 Snowmobile Forum

revrnd · 09-22-2003, 01:03 PM

When 'doo gave up on the ill-fated Monoshock & went to the C7 suspension. It looked similar to the original rear PRS suspension. Can anyone tell me what the differences were? I do know that the rear of my '95 MXZ 440 rode better than my '90 Mach 1.

Mikadoo · 09-22-2003, 08:00 PM

Not much and both will equally break your spine!

Blue2-dooGT · 09-22-2003, 08:23 PM

And what about the "Improved C-7" in the '95 GT? What was improved about it?

And what does the "C" stand for?

How about the "7"?

Thanks--been meaning to ask this.

Lasse · 09-22-2003, 09:10 PM

Hello

The only 1989 Formula that had the "Mono shock" rear suspension was the Mach-1
The Plus & Mx had the predecessor to the C7 which came on all Formula's 1992 - 94

Formula "PRS" chassi :

Rear suspension :
85 - 89 : C ? 146 mm / 5.75" travel ( Except Mach-1 1989 )
90 - 91 : Mono Shock 146 mm / 5,75" travel
92 : C7 153 mm / 6,0" travel
93 - 94 : C7 203 mm / 8,0" travel

Front suspension :
85 - 91 : 134 mm / 5,3" travel
92 - 94 : 153 mm / 6,0" travel

Ski stance :
85 - 91 : 920 mm / 36,2"
92 - 94 : 1010 mm / 39,8"

These dimensions does not include "Formula Mach-1 Racing" ( 1991 + 1992 )
Which had for an example M - 10 Rear suspension ( 260mm / 10" Travel) and completely different Front suspension ( 220 mm / 8,5" travel ),
It was also 25 Kg / 55 lbs lighter !!! than the ordinary Mach-1.

This Mighty Mach-1 is still a wonderful machine to drive with superb handling

SWRules

revrnd · 09-22-2003, 11:17 PM

Thanks Lasse. I also remember a MX-X in the PRS chassis ('91 or '92) that had a revised rear suspension. It had a smaller than normal diameter rear axle idler wheel to allow for more travel. I don't know how many of these sleds were built, other than it was run on the I-500 race in Minnesota.

oldyeller · 09-23-2003, 11:43 AM

I always used to take their "new and improved suspensions" with a grain of salt unitil I could actually try them out.I remember the day my 1988 formula Plus blew both its rear shocks.It rode way way better than it did when the shocks were new.Of course it had no rebound dampening if you went fast through the whoops but it was nice and plush over the rough stuff if you didn't ride to fast.In stock form it was like a rock.The 91 monoshock mistake.I don't even want to talk about that

revrnd · 09-23-2003, 12:12 PM

Heck, they screwed up the upper shock mount for the rear shock on the 90s. The suspension wanted to cycle farther than there was shock travel resulting in a bent mount. There was a service bulletin, not a recall to replace the mount (with the shock mounting tabs in the correct location) & a new (& improved :doh:

) rear shock. I don't remember if I noticed a difference in ride afterwards or not.

FreezerBurnt · 09-23-2003, 07:54 PM

Neighbour had the 91 MX-x,
great looking sled with pearl white hood and low black windhield :hallo1:

Chromoly parts and about 10lbs lighter woohoo

Good2Go · 09-23-2003, 08:22 PM

so what suspension would my '89 MX have? :l

~67x · 09-23-2003, 10:43 PM

A revision to the informative post by Lasse. The 91-92 Mach 1x as it was called did not utilize the Fast M-10 and front 8" travel but rather was an engine compliment in the form of twin pipes revised cylinders and other stuff. The x package in the 470 mx-x was a cross country/snow cross thing which was too tankish to compete with the Cats and Polaris of the day where as the x upgrade to the Mach 1s' was an ice oval derivative which was later superceded by the 93 Mach 670 single piper. The Mach 1x sleds were the balls in A stock ovals with Guy Useldinger and Mike Houle (sp?) doing the spanking. Them days are gone forever. Also in 93 there was a PRS based Plus x that was short suspended and ice freindly. Fast inc. was tight with Ski-Doo then and had a fine catalog that made you want to spend money. Doo ruled the ice around here during that era.

The monoshock 91 Mach suspension liked to bottom out in the bumps. The C-7 is pretty adjustable and while its alot more work than a modern cross sled skid it will take a pounding in the bumps. But, if you sit through the bumps youll take the pounding. C-7 transfers weight good therefor worked well in drags. Personally I liked the C-7 but Im no sitter. As you were.

Disclaimer: some of this data may not be 100% accurate.