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Best steering/suspension/brakes for 71 B body?
#2561109
10/08/18 10:09 PM
10/08/18 10:09 PM
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Joined: Sep 2006
Posts: 1,161
Los Angeles, CA
JF_Moparts
OP
super stock
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OP
super stock
Joined: Sep 2006
Posts: 1,161
Los Angeles, CA
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I have a 1971 Sebring that I Solo II autocrossed in the 1990's. To keep it on par with the new cars of the day I made the following mods to the car:
- Circa 1978 11.75" front disk brakes
- 205lb/inch torsion bars
- 1 1/8" front anti-sway bar
- Firm Feel steering box
- Fast ratio Pitman & Idler
- Poly bushings all around
- Heavy Duty rear leaf springs
- Subframe connectors, welded
All of which kept it competitive against cars of the 90s.
Then a few years back I added the Hotchkis upper control arms, shocks, and adjustable struts.
And now, well I've been saving up for some more modifications and wanted to ping the suspension brains here on Moparts for suggestions. Here's what I'm thinking of doing next, but I'm open to ANY suggestions:
- Borgeson steering box (w/ shorter stock Pitman/Idler)
- Rear anti-sway bar of some kind (I have a 1" bar on the shelf)
- Upgraded brakes of some kind
- New torsion bars, maybe a higher spring rate
- To get a little crazy, an Independent rear susp?
What do you all think? Thanks in advance.
Jim
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Re: Best steering/suspension/brakes for 71 B body?
[Re: JF_Moparts]
#2561175
10/09/18 12:03 AM
10/09/18 12:03 AM
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Joined: Nov 2008
Posts: 1,491
Lethbridge, AB, Canada
dangina
pro stock
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pro stock
Joined: Nov 2008
Posts: 1,491
Lethbridge, AB, Canada
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I use the fast ratio arms and the borgeson box, 1.8 turns lock to lock, you will have to put a different flow control valve on it (I bought the one off jegs but I'm thinking of enlarging it a little bit or going with a smaller pulley to make it easier to turn through the quick slalom) You will have to weld up the k member with all the extra forces applied to it if you haven't already. Also do you have inner fender braces, lower rad brace, subframe braces ect? if not I'd suggest that first. Rear sway bar is good (although some guys prefer to run without) I would go with bigger torsion bars and heavier spring rate on the rear. Dr. diff has a great rear brake kit that won't break the bank(and still use your stock ebrake cable) I've been looking and debating on the rear independant kits - If I do I would buy this: http://rick486.wixsite.com/dobbertinperformance
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Re: Best steering/suspension/brakes for 71 B body?
[Re: JF_Moparts]
#2561633
10/09/18 10:27 PM
10/09/18 10:27 PM
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Joined: Sep 2007
Posts: 14,889
up yours
Supercuda
About to go away
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About to go away
Joined: Sep 2007
Posts: 14,889
up yours
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What brand/model tires?
Radial T/A's, wasting your time.
Michelin Pilots, good street performer.
Hoosier slicks, ah no
MasterCraft SUV tire, lol
It does matter
They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.
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Re: Best steering/suspension/brakes for 71 B body?
[Re: JF_Moparts]
#2561884
10/10/18 12:41 PM
10/10/18 12:41 PM
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Joined: Jan 2010
Posts: 667
Los Osos, Ca
CKessel
mopar
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mopar
Joined: Jan 2010
Posts: 667
Los Osos, Ca
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Is that a MAGLEV setup like on the bullet trains?
Carl Kessel
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Re: Best steering/suspension/brakes for 71 B body?
[Re: JF_Moparts]
#2562151
10/10/18 09:50 PM
10/10/18 09:50 PM
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Joined: Feb 2010
Posts: 1,645
Phila. Pa.
Mattax
top fuel
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top fuel
Joined: Feb 2010
Posts: 1,645
Phila. Pa.
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I have a 1971 Sebring that I Solo II autocrossed in the 1990's. To keep it on par with the new cars of the day I made the following mods to the car:
'''
All of which kept it competitive against cars of the 90s.
....
And now, well I've been saving up for some more modifications and wanted to ping the suspension brains here on Moparts for suggestions. Here's what I'm thinking of doing next, but I'm open to ANY suggestions:
...
What do you all think? Thanks in advance.
Jim
What class do want to run in?
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Re: Best steering/suspension/brakes for 71 B body?
[Re: JF_Moparts]
#2564836
10/16/18 02:26 PM
10/16/18 02:26 PM
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Joined: Sep 2007
Posts: 14,889
up yours
Supercuda
About to go away
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About to go away
Joined: Sep 2007
Posts: 14,889
up yours
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What is your budget?
Best improvement, lightest rims you can get, fattest tires you can stuff into it. Good tires, really, really good tires.
They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.
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Re: Best steering/suspension/brakes for 71 B body?
[Re: JF_Moparts]
#2564937
10/16/18 04:46 PM
10/16/18 04:46 PM
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Joined: Dec 2003
Posts: 22,695
Bitopia
jcc
If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,695
Bitopia
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I forgot to mention them - 255/45-17s all around.
Jim
Get some bigger tires on it and get back to us. Those were fine a decade or so ago. You can't put too big of tire on a car that size if handling is your goal, even on the street 
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
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Re: Best steering/suspension/brakes for 71 B body?
[Re: JF_Moparts]
#2565085
10/16/18 09:32 PM
10/16/18 09:32 PM
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Joined: Jan 2003
Posts: 30,983
Oregon
AndyF
I Win
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I Win
Joined: Jan 2003
Posts: 30,983
Oregon
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255/45-17 is a decent size tire. It is way bigger than anyone had back in the 70's but way smaller than what BMW or Porsche engineers would put on a car your size these days. So you just have to decide how "modern" you want to be.
A 17 inch rim allows you to run a 13 inch brake rotor which should be big enough to stop that car. Do you know how much the car weighs and what the weight distribution is? If you haven't had the car scaled then that should be a high priority. You need to know what you're working with before you start working.
I assume the car is at least 4000 lbs and probably has 52 or 53% on the front tires. So there is a lot of weight up there which means the tires are getting tortured. A 255/45-17 tire can handle around 1500 lbs of load but that doesn't mean it is going to handle great when it is fully loaded.
Since you have a running combination you should be able to crawl underneath it with a tape measure and figure out if you can put a bigger tire on it. If you can great, if not then you know what your limitation is. If you are limited to a 255 section width then consider a bigger wheel. Perhaps a 255/40-18 or a 255/35-19 would work better for you. A 19 inch rim would allow a 15 inch brake rotor which is what the Porsche guys would use these days on a 4000 lb vehicle with 500+ horsepower.
Go spend some time on the BMW website and look at the tire sizes and brake rotor sizes they are putting on their 4000 lb cars. Or visit your local Dodge dealer and look at what the Dodge engineers put on the Hellcat Charger. That is a big car and they put big wheels, big tires and big brakes on it. Once you have the correct size wheels, tires and brakes then you can fine tune the spring rate and shock valving.
You'll also need to stiffen up the chassis a bunch. Ma Mopar made these cars as limp as a noodle back in the day. XV is out of business but you might be able to dig up some of the stuff they published on chassis stiffness. They were the only business to ever take the subject seriously but the market must not have been big enough to keep them in business. Basically you'll need to add some crossmembers and a monte carlo bar.
Last edited by AndyF; 10/16/18 09:34 PM.
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Re: Best steering/suspension/brakes for 71 B body?
[Re: AndyF]
#2565142
10/16/18 11:31 PM
10/16/18 11:31 PM
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Joined: Sep 2006
Posts: 1,161
Los Angeles, CA
JF_Moparts
OP
super stock
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OP
super stock
Joined: Sep 2006
Posts: 1,161
Los Angeles, CA
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255/45-17 is a decent size tire. It is way bigger than anyone had back in the 70's but way smaller than what BMW or Porsche engineers would put on a car your size these days. So you just have to decide how "modern" you want to be.
A 17 inch rim allows you to run a 13 inch brake rotor which should be big enough to stop that car. Do you know how much the car weighs and what the weight distribution is? If you haven't had the car scaled then that should be a high priority. You need to know what you're working with before you start working.
I assume the car is at least 4000 lbs and probably has 52 or 53% on the front tires. So there is a lot of weight up there which means the tires are getting tortured. A 255/45-17 tire can handle around 1500 lbs of load but that doesn't mean it is going to handle great when it is fully loaded.
Since you have a running combination you should be able to crawl underneath it with a tape measure and figure out if you can put a bigger tire on it. If you can great, if not then you know what your limitation is. If you are limited to a 255 section width then consider a bigger wheel. Perhaps a 255/40-18 or a 255/35-19 would work better for you. A 19 inch rim would allow a 15 inch brake rotor which is what the Porsche guys would use these days on a 4000 lb vehicle with 500+ horsepower.
Go spend some time on the BMW website and look at the tire sizes and brake rotor sizes they are putting on their 4000 lb cars. Or visit your local Dodge dealer and look at what the Dodge engineers put on the Hellcat Charger. That is a big car and they put big wheels, big tires and big brakes on it. Once you have the correct size wheels, tires and brakes then you can fine tune the spring rate and shock valving.
You'll also need to stiffen up the chassis a bunch. Ma Mopar made these cars as limp as a noodle back in the day. XV is out of business but you might be able to dig up some of the stuff they published on chassis stiffness. They were the only business to ever take the subject seriously but the market must not have been big enough to keep them in business. Basically you'll need to add some crossmembers and a monte carlo bar. Awesome response, thank you! I do need to get that car weighed. I've always assumed it weighed around 3500 lbs, based on nothing more than old Car & Driver articles and the fact that I have aluminum heads, intake, and lighter front seats! When I first moved to SoCal I assumed there'd be a huge drag / SCCA scene here, but as far as I can tell there's not too much due to the high cost of real estate gobbling up places where one might try to race. I think I can weigh the car at Irwindale. I do wish XV was back in business. Before I had any budget, all I was able to afford from them was their seat belts, which I still use and which were well designed. I also looked at the Corvette C5/C6 suspension site posted above, but you need to replace your entire rear frame to make that work. I want to keep the car somewhat original, so that's a no-go.
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Re: Best steering/suspension/brakes for 71 B body?
[Re: JF_Moparts]
#2565181
10/17/18 01:19 AM
10/17/18 01:19 AM
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Joined: Nov 2016
Posts: 200
Colorado
Bob J
enthusiast
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enthusiast
Joined: Nov 2016
Posts: 200
Colorado
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Look at US Car Tool Or XV Racing and Firm Feel This is a must read K Frame weldup My dash is out so I welded up the cowl pinch welds and the steering column Brace. The cowl use to flex pushing on the steering column brace before not so much now. The spot welds holds the car together but lets it flex a lot. Weld up as much you can. Tie the sub frame connectors to the set mounts. A lot of this is low cost with big returns and most will not show. It just takes time to prep and weld. Good luck as I like the 71 Plymouths as I had a 72 RR/GTX and a 71 RR.
Last edited by Bob J; 10/17/18 01:21 AM.
07 Porsche C2 997.1 6spd DD and SCCA Solo II SS
68 Plymouth GTX Convert. 493cu Hotkiss Wilwood Classic air, Building for Solo II Cam
65 Chrysler 300 Convert. project
57 Desoto 2dr. Firesweep 392 Hemi,Wilwood Project with son
2003 Dodge Dakota R/T "DEAD"
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Re: Best steering/suspension/brakes for 71 B body?
[Re: AndyF]
#2565439
10/17/18 04:38 PM
10/17/18 04:38 PM
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Joined: Sep 2006
Posts: 1,161
Los Angeles, CA
JF_Moparts
OP
super stock
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OP
super stock
Joined: Sep 2006
Posts: 1,161
Los Angeles, CA
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Nope, I didn't know about the book. It's now in my Amazon cart. To date, most of the info I've used for these susp mods has been Ehrenberg's tech articles in Mopar Action and 'Super Street Mopar' by Mike Martin.
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Re: Best steering/suspension/brakes for 71 B body?
[Re: JF_Moparts]
#2566564
10/19/18 04:55 PM
10/19/18 04:55 PM
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Joined: Jan 2010
Posts: 1,442
NW Chicago suburban area
Mopar Mitch
pro stock
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pro stock
Joined: Jan 2010
Posts: 1,442
NW Chicago suburban area
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JF -- You should be able to safely run 275-40-17 tires front and rear on 9"rims, such as the YearOne 17x9 Mopar rally rims.. as they have the correct offset to fit our cars... without any major concerns. And seek some 200 TW tires for that size.. choices are minimal from the different brands... 18s are where its at today for best selections.
Keep in mind that these shorter sidewall and diameter tires do change the ride comfort.. and watch out for potholes as the rims can more easily get damaged.
If you're not up to getting larger TBs, such as FF's 1.18 (and you wouldn't regret it... only wondering why you didn't get them sooner!), then get double-adjust shocks.. QA1 or Vikings.. or similar... double-adjustables.
Skip the exotic rear suspension that your thinking about... Hotchkis or FF rear leafs would suite your needs just fine.
Consider a larger rear sway bar beyond the typical .75"... look for or have made at least .875 or 1.0"... because your car is front-end heavy.
Have you re-positioned the battery into the trunk yet?... = about 1% weight transfer.
Mopar Mitch
"Road racers and autocrossers go in deeper and come out harder!"... and rain never stops us from having fun with our cars... in fact, it makes us better drivers!
Check out MOPAR ACTION MAGAZINE, August 2006 issue for feature article and specs on my autocross T/A!
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