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Front Subframe Strengthening


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#1 sovenmini

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Posted 24 November 2019 - 10:41 PM

Hi, I’m just about to start building up a new front subframe and will be building it for fast road / track days etc and I know that some people recommended stiffening up the subframe but just wondering If any one had done this before and the best places to add plates etc ? Any advice or pictures would help, many thanks

#2 wreckitralph

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Posted 24 November 2019 - 10:50 PM

tie bar mount  is a weakness

triangular plate in the corner to the tower  base

mabe two tubes from the top centre rear to the towers miglia style

seam weld the towers

 

this is not mine but perfect example

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Edited by wreckitralph, 24 November 2019 - 11:02 PM.


#3 sovenmini

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Posted 24 November 2019 - 11:27 PM

That’s super helpful thank you so much

#4 Retroman

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Posted 25 November 2019 - 10:08 AM

The subframe rear legs should also be plated underneath and its also worth plating the floor in car

 

Many that don't end up cracking the floor

 

Not sure if you are on a single bolt / rubber mounted subframe but they are bad for it



#5 Ethel

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Posted 25 November 2019 - 11:16 AM

Agree,

Plating the toe board for the rubber mounted subframe is the one job even a standard road car needs.

The tie rod mounts themselves are ok, there's just too little area for weld to attach them. A gusset helps, but half the size of the rusty photo (by edge length) should be more than adequate. The tie rod's only going to transmit forces along its length & the reaction forces will be along a parallel path in the subby - there's already a big chunk of steel in the right place, that the engine mounts bolt to. Otherwise eliminate any sharp internal angles that will be stress risers.

#6 wreckitralph

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Posted 25 November 2019 - 11:29 AM

agree and i should have said    in fact the toe board is probably the weakest area on a rubber mounted subframe wich i assume you have  i have a brand new toe board ive taken the square reinforcement plate off as ime going to fit my own larger thicker plate here


Edited by wreckitralph, 25 November 2019 - 11:42 AM.


#7 sovenmini

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Posted 25 November 2019 - 11:36 AM

Thanks for all the info, very helpful. It’s a mk1 so solid mount already but will plate anyway.

#8 wreckitralph

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Posted 25 November 2019 - 11:38 AM

this is not mine but shows the strengthening now ime not sure wether inside would be better for the plate instead of outside most plate the inside 

for strength i think the outside   i dont suppose a 2 mm plate is going to make a big difference in terms of the subframe mount being pushed further forward if on the outside ? i would also think the bolt holes on the mount have enough of a clearance to allow for  it somewhat

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Edited by wreckitralph, 25 November 2019 - 11:41 AM.


#9 Cooperman

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Posted 25 November 2019 - 12:21 PM

The front sub-frame is somewhat over-engineered as it is. For road or racing use there is no need to reinforce it or seam weld it.

Even for tarmac rallying, the only strengthening I do is to weld triangular plates onto the tie-bar 'ears' to prevent them bending back.

Unless a car is subjected to serious abuse on rough rallies no more additional strengthening is needed.

The MK.1 mounting areas are strong, unlike the rubber-mounted foot-well bulkhead area which will bend. For competition with a later shell that must be reinforced and solid mountings fitted.






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