IRS or swing axle?

[j-f]

Hello,

I'm completing my next project on a 58 sedan. It's a real puzzle. I buy the body without shelf  last years, doors, decklid and interior this winter etc...

Engine will be something like a 1915 with W125 or Fk8 - 1.4. The car will be treats as a 70's cal look.

I have a late 70's shelf. But, I was wondering if an IRS will not be better? Which gearbox is stronger? 

[Neil Davies]

I'd be tempted to build it swing axle if thats what bits you've got, but weld in the mounts for IRS into the pan just in case you want to change at a later date - saves blowing the car apart again to do more welding on the pan. 

[Zach Gomulka]

IRS weighs about 40lbs more and has more parts to break. But it does handle much better and keeps the tires flat on the ground when you launch. Six of one, half dozen of the other...

[j-f]

OK. Thanks.

That's 2 good answers.

Good Idea Neil to weld the the IRS mount on a swing axle shelf, "just in case" . 

And Thanks Zach for the info. I thought that an IRS was not good for 1/4 mile . But, that's logical. IRS don't makes this /  \ at launch.

I was planning to use 924-944 steel rear arm to have from a simple way rear discs brakes and use the 944 front brakes.
 But I don't know if it's useful on a such car? I plan to use it as a weekend warrior with some strip action. (I'm not far from Bitburg, so I can race sometimes on a year).

[Black Sheep]

I.R.S tends to make more sense at the top end when you come off the power , OK it weighs more but Ritchie Webb put his cab in the 9's and that is no light car ! as for 944 arms on a early car its gonna put the wheels right out in the arch's and that will affect your decision on wheel and tyre size . personaly I run IRS with a 901 box with 20mm narrowed Arms on the 49 and I find this works just fine , if you do decide to weld in the mounts dont forget to clearance the rear forks for the IRS CV's .
Good luck .

[qubek]

I thought that there are various types of 924/944 rear arms, steel and alu, narrow and wide, and that you can find one being at the same time narrow (Bug size) and alu.

[nicolas]

irs is overall a better design and if you break something most of the time it is the CV joint and not the gearbox. mark herbert was in favour of te IRS after he rolled his black bug with swingaxles.
swings are very good as well and have been favoured by dragracers for a long time. it is more nostalgic to run it if you are after that. but equally a lot of early shells were put on a later chasis...
as far as gearboxes are concerned, both can be made as strong, but the later IRS have stronger first and second (some) so that is an option.
i have a IRS in the squareback and am not happy with the so called benefit of them over the swinaxles. my fastback (swing) hadles better then the IRS square. i am even thinking of reversing it and putting it back to a swingaxle. the main problem is that the arms are not alligned like they should and the wheels have some serious negative camber.

but the idea of welding in the brackets is a good idea and if you make up your mind you can go either way. and switch if you want

 

[Sam K]

The one thign nobody mentioned yet is how much easier it is to change IRS trannys. I've blown 11 swingaxles in my '67. 9 of them were supposedly "built" trannys too. That's why my future race bug is a 63 on a 73 pan and it will have a bus gearbox and porsche 930 CV's. I'm not fooling around with this one!

[Neil Davies]

The one thign nobody mentioned yet is how much easier it is to change IRS trannys. I've blown 11 swingaxles in my '67. 9 of them were supposedly "built" trannys too. That's why my future race bug is a 63 on a 73 pan and it will have a bus gearbox and porsche 930 CV's. I'm not fooling around with this one!

I know of people who A-frame race cars, have broken CVs or axles and still been able to A-frame the car home. Can't do that with swingaxle!

[Zach Gomulka]

I hate having to dig into the CV's... fucking grease everywhere!

[Bernard Newbury]

I have raced my car with both swingaxle and IRS(091 box) and prefer IRS. I had a few axle breakages last year due to a well prepped track and new slicks but have now changed to Porsche 930 with lightened cvs and rifle drilled 300m axles. It feels a lot more stable at the top end and the added advantge of not having to set the rear end up every time you take the tranny out. Bernie

[j-f]

I have raced my car with both swingaxle and IRS(091 box) and prefer IRS. I had a few axle breakages last year due to a well prepped track and new slicks but have now changed to Porsche 930 with lightened cvs and rifle drilled 300m axles. It feels a lot more stable at the top end and the added advantge of not having to set the rear end up every time you take the tranny out. Bernie

Thanks all to share your opinions. 

That's was what I though.

I will go for an IRS. 

[benssp]

I have raced my car with both swingaxle and IRS(091 box) and prefer IRS. I had a few axle breakages last year due to a well prepped track and new slicks but have now changed to Porsche 930 with lightened cvs and rifle drilled 300m axles. It feels a lot more stable at the top end and the added advantge of not having to set the rear end up every time you take the tranny out. Bernie

Axle changes now take minutes, between me and bernie we can change an axle before carols made the tea! hopefully the new setup is bulletproof, only time will tell

[Rennsurfer]

The one thign nobody mentioned yet is how much easier it is to change IRS trannys. I've blown 11 swingaxles in my '67. 9 of them were supposedly "built" trannys too. That's why my future race bug is a 63 on a 73 pan and it will have a bus gearbox and porsche 930 CV's. I'm not fooling around with this one!

Excellent post on all points. I haven't heard of anyone using 930 c.v. joints since the old days. They're not cheap... but, ya get what ya pay for.

[benssp]

Type 2 c.v's work well on a car with less horses than bernies 300-400, offer to buy a friend with a van new C.V's and use worn original T2 units

I think Richie Webb is using Porsche 944 C.Vs

[Zach Gomulka]

After rebuilding my own axles and type 1 CV's, Im scared to even peel out! Those things dont look like they should be able to handle stock hp I think type 2 CV's will be in my future...

[SteveW]

Type 2 c.v's work well on a car with less horses than bernies 300-400, offer to buy a friend with a van new C.V's and use worn original T2 units

I think Richie Webb is using Porsche 944 C.Vs

Yeah he said to me use 944 Stub axles with 944 cv's at the axle end and stock bus ones at the box end!

Steve

[Steve D.]

As long as you don't have an offroad car, stock cv's will take way more abuse than you think.  The angle of the axle is what makes the cv work- any normal ride-height car is going to put the cv's almost perfectly perpendicular with the axle.

250+hp with a puck clutch is probably close to the limit of a stocker, more with a rag disk.

[Torben Alstrup]

250 hp with stock CV´s would be pushing your luck IMHO. But with 181 (100mm inner CV´s and 80 mm outer) axles it works. I have personally been into that. Approx. 230 hp on a 1910 T4 with a solid shoot of gazz. (the tranny broke before the axles.) And a similar hp 2386 NA. No problems. What you need to do is to buy raceware hubs. The stock will destroy the shafts in about a season.
And I´m ALL with Bernie. The car is much more steady at the end of the track, when you let off the throttle. If I was to race again, I would definitely use IRS despite the extra weight.
T

[Neil Davies]

This is a really good discussion, with lots of good information. So, can we decide on an ultimate combination for a sensible budget car? Assume an 091 bus box (it's what I want to put in the '51 anyway!)

What seems to be favourite at the moment is Porsche 944 stub axles and CV joints at the wheel end, stock bus CVs at the box end. Bugpack I know do the weld-in brackets to convert a S/A pan to IRS. Glenn (49-rag) said about 944 arms widening the track by about 20mm. What arms do we go for then? 924? Stock 1302/1303?

[SteveW]

I'm going to use stock bug A Arms which are the single spring plate type as they are lighter than the double type! Not sure if they are the best but i'd heard about porsche arms widening the track!

[Bernard Newbury]

What seems to be favourite at the moment is Porsche 944 stub axles and CV joints at the wheel end, stock bus CVs at the box end. Bugpack I know do the weld-in brackets to convert a S/A pan to IRS. Glenn (49-rag) said about 944 arms widening the track by about 20mm. What arms do we go for then? 924? Stock 1302/1303?

I used modified  stock A arms, 930 chromoly output flanges, 930 chromoly stub axles, 930 lightened GKN CV's (chromoly cages) and the axles were custom made in the States out of 300m. Unfortunately not the cheapest way round it but hopefully it will last  a bit longer then type 2. None of it is  Empi as I think Empi CV's, stub axles etc are Chinese. Type 2 lasted quite a while but as the traction got better then they kept breaking.  Bernie

[71CALRIPPER]

may have some 930 CV joints for sale with CM cages if anybody is interested

[SteveW]

What seems to be favourite at the moment is Porsche 944 stub axles and CV joints at the wheel end, stock bus CVs at the box end. Bugpack I know do the weld-in brackets to convert a S/A pan to IRS. Glenn (49-rag) said about 944 arms widening the track by about 20mm. What arms do we go for then? 924? Stock 1302/1303?

I used modified  stock A arms, 930 chromoly output flanges, 930 chromoly stub axles, 930 lightened GKN CV's (chromoly cages) and the axles were custom made in the States out of 300m. Unfortunately not the cheapest way round it but hopefully it will last  a bit longer then type 2. None of it is  Empi as I think Empi CV's, stub axles etc are Chinese. Type 2 lasted quite a while but as the traction got better then they kept breaking.  Bernie

Bernie, which A Arms do you use? 1303? or are they all the same? I've found some at a good price but the seller only knows they come from a beetle!

Cheers
Steve

[richie]

Steve,theres early and late,the late being the single spring plate version,the easiest way to tell is the mounting holes for the spring plate form a triangle on the early ones[same as swingaxle],but 1 hole is offset on the later ones
cheers richie,uk

[SteveW]

Steve,theres early and late,the late being the single spring plate version,the easiest way to tell is the mounting holes for the spring plate form a triangle on the early ones[same as swingaxle],but 1 hole is offset on the later ones
cheers richie,uk

Ah cool these are single spring plate type I've found! £30 for both arms!

Cheers
Steve

[richie]

Steve,theres early and late,the late being the single spring plate version,the easiest way to tell is the mounting holes for the spring plate form a triangle on the early ones[same as swingaxle],but 1 hole is offset on the later ones
cheers richie,uk

Ah cool these are single spring plate type I've found! £30 for both arms!

Cheers
Steve

   Thats all you need,cheers richie,uk

[SteveW]

Steve,theres early and late,the late being the single spring plate version,the easiest way to tell is the mounting holes for the spring plate form a triangle on the early ones[same as swingaxle],but 1 hole is offset on the later ones
cheers richie,uk

Ah cool these are single spring plate type I've found! £30 for both arms!

Cheers
Steve

   Thats all you need,cheers richie,uk

Thanks dude 

[Bernard Newbury]

Steve,theres early and late,the late being the single spring plate version,the easiest way to tell is the mounting holes for the spring plate form a triangle on the early ones[same as swingaxle],but 1 hole is offset on the later ones
cheers richie,uk

Ah cool these are single spring plate type I've found! £30 for both arms!

Cheers
Steve

   Thats all you need,cheers richie,uk

Thanks dude 

Thanks for the replies Ritchie. I was going to suggest you would know as Marko did the job and I did not ask what A arms he used. When are you home? Bernie

[richie]

Steve,theres early and late,the late being the single spring plate version,the easiest way to tell is the mounting holes for the spring plate form a triangle on the early ones[same as swingaxle],but 1 hole is offset on the later ones
cheers richie,uk

Ah cool these are single spring plate type I've found! £30 for both arms!

Cheers
Steve

   Thats all you need,cheers richie,uk

Thanks dude 

Thanks for the replies Ritchie. I was going to suggest you would know as Marko did the job and I did not ask what A arms he used. When are you home? Bernie

Last night cheers richie