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Old 30th July 2009, 14:50   #61
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Originally Posted by ex670c View Post
2) Maybe your steering is not setup properly.
It was Jammy's Jeep, not mine.

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Originally Posted by ex670c View Post
3) Broader tyres reduce the steering re-centering.
So wider tyres can cause problems.
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Old 30th July 2009, 15:14   #62
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Originally Posted by DHABHAR.BEHRAM View Post
I am working out the result with the formula with 5.38 and let's see what happens. I will give you the resultant shortly.
Hello sir,

As per your formula for an XD3P with 5.38:1 Diff-Ratio and 31" tall tyres.

80Kmph @ 3000rpm.

If LP1109 ex-army wheel disc's are considered then suitable king-pin upgrades must be considered as these are 13.5kgs to a JEEP's 9Kg wheel Disc.

Also the suspension will behave like that of a heavier vehicle i.e Tata407/ FJ460DS433 range.

Please correct me if I am wrong.

Regards,

Arka
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Old 31st July 2009, 18:11   #63
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How often do you ground a 80 inch wheelbase Jeep Nitrous to warrant an elevation?
Again, been taking too many hits on the underside of late. I'm thinking the additional 2 inches from a tyre upgrade ought to be a great start.

Raising a Jeep's ground clearance : Options?-beached-classic.jpg

No SPOA at the moment.

Quote:
1) Power - XD3P

2) Better Suspension - Uprated shocks

3) Taller Tyres - maxxis 31-10.50-15

4) TRACTION AIDING DEVICES - Dog-Clutch LSD
Will do as per your advice, man!
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Old 31st July 2009, 21:56   #64
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Again, been taking too many hits on the underside of late.
These ridges are nasty. Shams managed to ground his CJ3B at our initial OTR at Vikharabad featured in this thread, had to pull him out with my 207. But that happened primariy as he approached it perpendicular.

This past OTR we encountered a similar double ridge in a field which I knew I would ground the CJ3B in the centre were I to take it on at anything but an acute angle. It seesawed over, literally, and managed to clear it without touching.

Your plan to take it to a 31 incher sounds fine. Its great to see you give that Jeep a good workout!

Perhaps some of the experts here can list a table vehicle wise on height increase vs poorer centre of gravity vs roll over angle. The fact that vehicle dynamics go for a toss with each inch it rises is another issue altogether which may not be quantifiable

Last edited by DKG : 31st July 2009 at 22:02.
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Old 31st July 2009, 22:28   #65
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This post is not meant for the many experts we have in our midst but for those who are curious.

There is a method of calculating the centre of gravity for your vehicle. The single most important factor affecting roll over is your centre of gravity which is a imaginary point of concentration of masses distributed in the space of your vehicle.

In offroad conditions as your vehicle encounters either a forward or backward, left or right slope the vertical line passing through the centre of gravity shifts within the four corners of your tyre contact patch. In any condition if the line crosses outside the patch formed between your four tyres your car will roll over. Simply put the lower the CG the lower the chance of roll over. The higher you go easier to tip over.

SPOA "degrades" the centre of gravity dramatically as it totally realigns the distribution of masses in the car space and it is foolish to attempt this as you severely compromise your roll over angles. Unless ofcourse you are redoing the wheelbase and track amongst a few things to offset the compromise to CG on account of height increase

Some of the factors affecting your centre of gravity are your wheel base, your track, the weight of the axle up front and back. I am not an expert in this but Mr. Dhabhar can possibly share the equations that enable one to actually calculate the CG for your particular vehicle.

All of us can hop down to our local weigh bridges and do some measurements to figure this out and actually tabulate your roll over angles. Ofcourse you need some ramps to lift the wheels up from the contact patch to calculate how the CG shifts.

In summary do not raise your car unless you actually calculate and are fully aware of the compromise to your roll over angles.

A great part of offroading entails handling obstacles that entail sharp inclines. Please please remember that with each inch that you raise your Jeep you are compromising your roll over angles.

BTW the centre of gravity is very dynamic and even people sitting in your car can affect it. So changing engines, more people in the car than what you are used to, anything can throw you off guard as far as your CG and how your car behaves. The fact that your Jeep handled a particular slope well when you were alone won't mean it wouid behave the same when you have all your family or friends in it. Weight transfers can play riot with CG. So ! guys just be careful when your ride height changes. Why do you think Ferrari and Lamborghini have their cars so low? Its all about good old CG and ofcourse aerodynamics.

Last edited by DKG : 31st July 2009 at 22:47.
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Old 31st July 2009, 23:18   #66
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GTO please excuse me for posting in different posts but basically I went from talking with you to non experts hence the differentiation

Here are some of the ways to positively impact your centre of gravity

1. Increase track

2. Increase wheelbase

3. Lower the weight of items in vehicle ( please note only those above the CG)

4. Try to do away with things, ie lesser weight ( again those items that lie above CG)

5. Pay special attention to weight beyond the wheelbase eg winches, spare tyres. These have a multifold impact on CG position shift. For example a winch up front reduces the weight on the rear axle and increases weight on the front axle. The total effect on CG of a weight beyond the wheelbase is multiplied as compared to what it is when the weight lies within wheelbase.

Lower tyre pressures generally lowers CG but one downside is that on a slope the track gets marginally reduced as the lower tyre (on the slope) tends to tuck inward. So you need to strike a balance.

Please note that the ideal position of the CG is in the centre of the vehicle and as low as possible. Heavy engines and big winches move it right up front. If you haven't balanced the CG imagine what that will do when you are going down a steep slope. The car will roll over forward. The scary part is the slope may appear not too steep but if the CG in your car is such that the minute you tip into the slope the line through CG moves ahead of the front axle you will have your rear coming up over you causing a instant forward tumble.

In summary it makes sense to invest in a roll bar if you are planning on raising your car. Actually for anyone attempting on the limit offroad maneuvres its advisable to add a strong roll bar and seat belts.

If you are a trail monkey like me who is not into mods then the stock vehicle will do just fine.

Last edited by DKG : 31st July 2009 at 23:31.
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Old 1st August 2009, 11:28   #67
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Again, been taking too many hits on the underside of late. I'm thinking the additional 2 inches from a tyre upgrade ought to be a great start.

No SPOA at the moment.

Will do as per your advice, man!
Hi GTO,

This is quite OK, as long as you have you skid plate.

While on OTR if you feel the skid plate touching, give the throttle a sharp tap, and the skid plate will do the JOB.

The JOB is sliding over the obstacle rather than, getting the naked cross member stuck.

Regards,

Arka.

PS - I never give advice, I STRONGLY Suggest
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Old 1st August 2009, 14:32   #68
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That's some information you listed there, DKG. Thanks!

In the meantime, I've been having some talks with Arka. Am posting the PMs here (with his permission) since his advice will surely be of help to others:

Quote:
Originally Posted by ex670c
Hi Rushabh,

SPOA makes sense only if you want more rubber on the wheels and under the diff.

Why do we want for GC for better maneuverability.

Why maneuverability, because with open diff's we need to place the tyres better.

working back wards - Lock the diff.

Some problems

The Steering is vague, I helped XXXXX in his SPOA for his MM540 (Munnar), particularly pinion pitch.

Recurring transmission and leaf spring related issues.

SUA leaf springs will sag in no-time.

In a SPOA setup your
1) Tie-Rod and drag links are exposed.

2) Fabricate a rear traction bar and set it up.

3) Its not easy to fabricate Hi-Steer Arms for the JEEP Closed Knuckle, more difficult for OKBJ.

4) Differential Pinion Angle - this can make or break the entire setup.

We can address 2 & 4 , 1&3 go hand in hand.

Also I have not seen a SPOA vehicle perform reliably in a long distance OTR. Even in the 36kms (up & down) Munnar trail, Manzoor popped his rear axle in 10kms.

This is a FFRA Dana 44. Not a Gypsy or SFRA.

I'm not against SPOA, just that its not worth the headache, its like treating the symptom and not the disease.

If its the BLING factor, thats a whole different issue.

My suggestion is go for a

1) Rear auto locker and front LSD with broader Axles
1a) Check you FIP

2) Change to Maxxis M8080 31-1150-15 tyres.

3) Do not change you're differential ratios yet.
3a) Better shocks.

4) then Change to SPOA (after 6months - 1 year)

Regards,

Arka

PS- You have a very well maintained and precious M&M CLASSIC don't kill her. Upgrade the hardware, its no big deal since you travel a lot.
Quote:
Originally Posted by ex670c
Hi Rushabh,

Skyjacker and couple of others make Suspension Lift kits for the CJ3B/CJ5 cost USD600 odd.

Even simpler Stiffen the CLASSIC leaves to Civilian CJ3B pack and add better shock for rebound.

Military CJ3B 10F 11R - Leafs
CLASSIC - 8F-9R Leafs
Civilian - 9F-10R Leafs

As an export model The CLASSIC had lesser leaves to compensate for harsh ride, draw back was the leaf sags very fast.

OEM civilian CJ3B leaf pack for same eye to eye length rides 1-2inches taller. The catch is rebound, the regular shocks dampen but insufficient rebound.

Bilstien cost 8K each landed in India.

USA they cost 3.3K each.

Regards,

Arka

PS - Also change the body beds to MM540 style you will gain 1 inch height and better cushioning.
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Originally Posted by DKG View Post
Perhaps some of the experts here can list a table vehicle wise on height increase vs poorer centre of gravity vs roll over angle. The fact that vehicle dynamics go for a toss with each inch it rises is another issue altogether which may not be quantifiable
This, along with the loss of potential reliability, is why I am not considering an SPOA. Period. I do some pretty crazy stuff on the hills, rolling over = catastrophic outcome. I have put a lot of effort in getting my Jeep to where she is today. The best part about her is her chuckability (off the road) and reliability. Not wanting to mess with that.

For the time being, I am adhering to Behrams and Arkas advice. Will open a new thread (or update this one) with stage-by-stage details.

@ V-16 : The biggest benefit of SPOA is that it allows you to put larger tyres than possible in stock configuration. Larger diameter = better ground clearance (even the diffs are higher).
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Old 2nd August 2009, 10:33   #69
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Originally Posted by DKG View Post
... There is a method of calculating the centre of gravity for your vehicle. ...
Not very long back I came across this GREAT article on CG & roll over angles.

Here is a cross post from my SPoA thread:

Quote:
PS: for Center of Gravity, here is a great article on what it means and what all comes into play when we say 'CG'.

Center of Gravity and Roll-Over Angle - Jeepaholics Anonymous
Also attached is an excel sheet with provision to calculate CG & RoA for one's vehicles
COG_ROA.xls

Quote:
SPOA "degrades" the centre of gravity dramatically as it totally realigns the distribution of masses in the car space
  • Yes, the SPoA does alter CG. No 2 ways about it.
  • However, even bigger tyres by same logic do alter CG and one should not just assume that bigger tyres are 'safe' (purely from CG & RoA viewpoint).
Quote:
and it is foolish to attempt this as you severely compromise your roll over angles.
A better way to make this point could be -- 'please be VERY careful' before doing this mod job as this can -ve'ly impact your RoA

Calling it foolish is not called for -- whatever that person may or may not be trying to achieve.

Last edited by khan_sultan : 2nd August 2009 at 10:43.
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Old 2nd August 2009, 22:18   #70
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Originally Posted by GTO View Post
For the time being, I am adhering to Behrams and Arkas advice.
Wise decision

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Originally Posted by khan_sultan View Post
  • However, even bigger tyres by same logic do alter CG and one should not just assume that bigger tyres are 'safe' (purely from CG & RoA viewpoint
True but you will also notice that most people upgrading to taller tyres go for wider too. I suppose if they are using rims with a built in offset then your track is actually increasing which may compensate to an extent for the CG being altered.

Quote:
Calling it foolish is not called for -- whatever that person may or may not be trying to achieve.
There are many Jeep owners whose criteria in doing up their Jeep is LOOKS or as Arka put it in his mail to GTO the BLING factor !!! Now such people who opt for SPOA because they feel with huge tyres and elevated body it looks butch, without understanding the dramatic compromise to roll over angles are most certainly doing a very foolish thing if they ever venture offroad with their car modded so.

My statement should not be misinterpreted to read that anyone opting for SPOA is a fool. Thousands of enthusiasts the world over opt for that mod. Just take a look at all the slush fests and the jacked up trucks. To them the body not bottoming out in slush is top priority.

I'm sure many here at TBHP have tried this mod. I sincerely hope they know the compromise to their factory spec roll over angles.

Today when I was out in the wild negotiating some wild inclines I was only in awe of the brilliant balance of the CJ3B in some seemingly scary conditions. Lets all give the original designers of the Jeep some credit for knowing what they did. Please don't forget this machine was built only for offroading (definitely not for highways ). That was the mandate. Believe me if SPOA had more merit than demerit all Jeeps ever manufactured would ride on stilts.

Last edited by DKG : 2nd August 2009 at 22:23.
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Old 3rd August 2009, 15:16   #71
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Dear DKG - ref your last paragraph in your last post above, you are ABSOLUTELY CORRECT. The original CJ3B vehicle at 80" wheelbase and 48" wheel track is a gem to drive and it handles beautifully. Those guys knew exactly what they were doing.

Best regards,

Behram Dhabhar
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Old 3rd August 2009, 15:46   #72
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Those guys knew exactly what they were doing.
Thanks for affirming that Mr. Dhabhar. I am just glad I can recognise a good design when I see it !!

The Hummer and Mahindra Axe seem to also validate the point made earlier of the need to increase both track and wheelbase should one desire a taller GC without compromising roll over angles (affected by the CG)

Last edited by DKG : 3rd August 2009 at 15:47.
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Old 3rd August 2009, 16:55   #73
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I didnt post in this thread as 4wd heavy weights were speaking until now. Having said that iam the guy who believes stock is the best setup!

As very wisely written, those guys who designed original 3B knew what they were doing. Hence it is wise not to touch anything! Maximum take an alternate route if that do not work for you. Most of the landscape is easy for 3B to conquer unless you want to try to attempt particularly a difficuilt one by choice. Altering vehicle dynamics beyond a particular level is not advisable as you are crossing limits.

Taller tyres seem to be the best option followed by 1-2 inch shakle lift.
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Old 3rd August 2009, 17:15   #74
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This is a really great discussion and given that it is (mostly) in plain English all the more interesting for someone like me who is interested in getting the best out of the vehicle.

Thanks to all. I would be watching this thread keenly.

Warm regards
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Old 4th August 2009, 06:55   #75
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Originally Posted by DHABHAR.BEHRAM View Post
Dear DKG - ref your last paragraph in your last post above, you are ABSOLUTELY CORRECT. The original CJ3B vehicle at 80" wheelbase and 48" wheel track is a gem to drive and it handles beautifully. Those guys knew exactly what they were doing.

Best regards,

Behram Dhabhar
Behram, I agree with you 100% that the original CJ3B was a gem. I wish that M&M continued to make the original instead of trying to 'improve' it with the Classic.
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