450/451 Suspension interchange?

[THEDON]

Has someone tried or has info on interchangeability of front and rear suspension parts between the 450 and 451?

-Can you bolt a 451 control arm, steering knuckle, strut to the 450? I assume you will need to change the tie rod ends too.
-Can you bolt a 451 rear wishbone on a 450 rear subframe? Is the 451 rear wishbone wider than the 450 one?

If anyone has some info it would be great.

[Thrumbleux]

No need for any of that.
Go tried and tested spring and tyre route that is known to work and will still clear the bodywork - which a 451 rear axle (devoid BTW of an anti roll bar) wont.

[THEDON]

Ok thanks Thrumbleux no need... but, you are telling me that you have worked on those cars for 20 years and nobody tried to bolt on a seemingly more modern/better design maybe lighter weight to the 450.
Why did MCC Smart go through all the hassle and cost of designing new suspension parts if they are not better?

[Thrumbleux]

Front suspension on later fortwos was grafted from a C-Class Mercedes - lighter?

MCC Smart departed early days and from thereon Mercedes made the decisions, mostly disastrous ones. Compare how Mercedes handled the smart brand with BMW's success with mini.

[mikerj]

Why did MCC Smart go through all the hassle and cost of designing new suspension parts if they are not better?

Manufacturers strive for one thing above all others: low cost. Integrating a conventional lower balljoint into the wishbone is undoubtedly cheaper than manufacturing the original type, and eliminates the two bolts attaching it to the upright. Likewise the track rod end balljoint is now a conventional design which eliminates another two bolts holding it to the upright. The strut attaches to the upright with a single pinch bolt, rather than the three bolts required originally. The hub/wheel bearing is how a cheaper assembly since it's pressed into the upright rather than coming with a separate bolt on bearing housing. The upright itself is a single cast part rather than the fabricated/pressed metal design on the older car. All cheaper to make and cheaper to assemble.

[Thrumbleux]

And already in production for the C-Class, no new cost, existing cost amortised within huge volume C-Class sales.

[THEDON]

Thanks mikerj and Thrumbleux, good information. They are Mercedes parts and are cheaper to manufacture... Will they bolt to the 450? Is the 451 upright lighter than the 450? Is the 451 rear axle wider than the 450?

[Thrumbleux]

Doubt that the 451 upright is lighter - it fits the heaviest of C-Class - circa 1800kg. Don't know if it fits or not. Anti roll bar attachments are different.
451 rear axle is wider (has no anti roll bar provision a retrograde step) and a different shape (less angular) but compels you to use 451 wheels unless you go wide arch.There were wide arch kits but pretty rare now and likely to be very costly if you can even find for sale. Lots of money, very little gain, indeed a loss without rear anti roll bar - to which a 450 is very responsive (from 11mm to 13mm bar, a noticeable change in handling).

[mikerj]

The front suspension mounting points do look very similar, but I don't know of anyone that has fitted the 451 parts to a 450. If it does you'd need to make sure that the steering geometry hasn't changed i.e. are the steering racks the same width and are they mounted in the same location with respect to the uprights. I doubt there is much to be gained here though, the original 450 stuff is not very heavy.

I am 99.9% certain the 451 axle will not fit without a lot of cutting and welding, there are so many differences. If you want a wider axle (rather e.g. using wheel spacers) you could quite easily space the the entire wheel bearing/drum assembly out from the standard axle, but this would mean you'd need longer driveshafts.

[Thrumbleux]

The front suspension mounting points do look very similar, but I don't know of anyone that has fitted the 451 parts to a 450. If it does you'd need to make sure that the steering geometry hasn't changed i.e. are the steering racks the same width and are they mounted in the same location with respect to the uprights. I doubt there is much to be gained here though, the original 450 stuff is not very heavy. Lightweight 15 inch wheels rather than heavy 16/17s would be an easy win here.

The only interchange I have ever heard of was a guy on Smartz (years ago) who fitted a 450 anti roll bar to a 450 as he wanted more roll stiffness on the front. The different pick-up points on the two cars dictate different bar diameters for the same (or similar) roll stiffness thus the thicker 450 bar in conjunction with 451 pick-up points gave him his desired result.
Agreed, 450 parts are as light as they can be - wheels also, especially the steels.

I am 99.9% certain the 451 axle will not fit without a lot of cutting and welding, there are so many differences. If you want a wider axle (rather e.g. using wheel spacers) you could quite easily space the the entire wheel bearing/drum assembly out from the standard axle, but this would mean you'd need longer driveshafts.

You've reminded me - does the 451 not have a 2'' longer wheelbase? Achieved with the axle (not chassis lengthening)?

[THEDON]

Good info. Lets forget about the back for now. I will need to buy a 451 front upright and compare...
Will keep you posted.

PS: if somebody has one laying around please let me know.

Thanks

[Thrumbleux]

If it does you'd need to make sure that the steering geometry hasn't changed i.e. are the steering racks the same width and are they mounted in the same location with respect to the uprights. I doubt there is much to be gained here though, the original 450 stuff is not very heavy.
.

The above x 100.

[Thrumbleux]

If I was to do anything with the front end (apart from the obvious lowering which I already have) this is what I'd do.
Arrange for a spherical bearing (ie Rose joint) to sit on the same axis as the other two (rubber) bushes and exactly between them. Thus, all lateral loads will be taken by a rigid joint while fore and aft compliance (which I'm not prepared to lose) is preserved.
All aspects of steering geometry would, with the above, be much better controlled.

[tolsen]

Fit the front transverse leaf spring if you are looking for softer suspension and better handling.

[Thrumbleux]

Fit the front transverse leaf spring if you are looking for softer suspension and better handling.

Or put your money in your back pockets to insulate your butt from the bumps. The price of a smart leaf spring is more jarring than driving across the moon in a coil sprung fortwo.

[tolsen]

Or put your money in your back pockets to insulate your butt from the bumps. The price of a smart leaf spring is more jarring than driving across the moon in a coil sprung fortwo.

Only £677.25 but likely cheaper from dismantlers.

https://www.smart-stuff.parts/450-front-leaf-spring-assembly

Less unsprung mass and nil chance of broken front coil springs.

[Thrumbleux]

Lower Gof G would IMO be the biggest benefit. Throwing your wallet on the floor would achieve the same though.