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freetors Nick H
Collinsville, OK, USA   USA
1973 MG MGB
In reply to # 3470258 by Thurlowb Changing springs is no problem. I've done that and know exactly what is involved. Right now, I'm running the 550lb "road lowered" springs. I assume I have to go right to the "race" 660lb springs to make a difference? Another 1/2" drop might be pushing the geometry a bit. Any other spring option you are aware of?

Is there any kind of spring insert that can be jammed into my springs to limit their travel? Safely?

I am going to lower another 1/2" or so with the new rims and tires...should help lower the COG anyway.

My mistake, I didn't realize you already had stiffer springs. I'm running on 550 springs as well but with the factory '73 swaybar.

Be advised that a stiffer FSB will generally promote understeer. Also if you run on bumpy lots the car might react less predictably. Not a problem on smooth lots though. Increasing swaybar stiffness basically turns the suspension more and more into a solid axle.

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Thurlowb Avatar
Thurlowb Silver Member Brad Thurlow
Coquitlam, British Columbia, Canada   CAN
The new wheels and tires are on. Silverstone IIs with BFG GForce Sport Comp 2 195/55 15s. I would have had to go to a 195/50 to get a 200 compound tire. This is my best attempt at compromise between general use, road noise, racing performance and looks. Since these will wear pretty quickly at 340 compound, I'll pop the Rostyle 14s back on for long highway trips.

As a bonus, each wheel/tire combo is almost 4lbs lighter than the 14" Rostyles. Looking forward to putting some serious wear on these in a week!



freetors Nick H
Collinsville, OK, USA   USA
1973 MG MGB
I've got the exact same tires, size and model, only on these wheels:


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Thurlowb Silver Member Brad Thurlow
Coquitlam, British Columbia, Canada   CAN
Nice...shiny...gold...

freetors Nick H
Collinsville, OK, USA   USA
1973 MG MGB
Brad, I've found from past events that these tires respond to spraying with water between runs. They get kind of greasy feeling as they warm up. But they still pretty darn well as long as you don't overheat then!

freetors Nick H
Collinsville, OK, USA   USA
1973 MG MGB
My fastest run in Neosho today. Last run so starting to get sloppy. It's also hard to drive fast when you're body is flailing around in a seat that offers little to no support.


Thurlowb Avatar
Thurlowb Silver Member Brad Thurlow
Coquitlam, British Columbia, Canada   CAN
Nice run...looked like fun! Do you ever need third gear?, or was it just that course that didn't need it?

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freetors Nick H
Collinsville, OK, USA   USA
1973 MG MGB
I was pretty much at the limit of second gear and not enough room to make upshifting worthwhile. Many courses will require shifts to third of second-OD to keep accelerating. This course just didn't have the room to wind it out.



Edited 1 time(s). Last edit at 2017-03-19 10:04 PM by freetors.

V8MGBV8 Avatar
V8MGBV8 Carl Floyd
Kinggsport, TN, USA   USA
In reply to # 3472421 by freetors I was pretty much at the limit of second gear and not enough room to make upshifting worthwhile. Many courses will require shifts to third of second-OD to keep accelerating. This course just didn't have the room to wind it out.

What is your RPM threshold?

Over the years, I have driven very few courses that really required third gear. Sometimes, rather than lose time with up to 3rd & back to 2nd, I will leave it in 2nd & watch the tach go to 6200-6300, occasionally 6500.

Thurlowb Avatar
Thurlowb Silver Member Brad Thurlow
Coquitlam, British Columbia, Canada   CAN
In reply to # 3472808 by V8MGBV8
In reply to # 3472421 by freetors I was pretty much at the limit of second gear and not enough room to make upshifting worthwhile. Many courses will require shifts to third of second-OD to keep accelerating. This course just didn't have the room to wind it out.

What is your RPM threshold?

Over the years, I have driven very few courses that really required third gear. Sometimes, rather than lose time with up to 3rd & back to 2nd, I will leave it in 2nd & watch the tach go to 6200-6300, occasionally 6500.

Ouch! I haven't replaced my engine or made any mod that would enable higher revs...so my redline is still 6000 (ignoring the shaded redline that starts at 5500).
I'm never going to win, so one of my primary goals has to be to "not destroy the car". So I don't want to push it past 5000 if I can help it. I'm comfortable with the extra shifting. I'm just having more fun that the rest of the drivers! Besides, looks like I'll always win 1st in class.

Brad

Thurlowb Avatar
Thurlowb Silver Member Brad Thurlow
Coquitlam, British Columbia, Canada   CAN
My new front anti-sway bar arrived. Got that installed. (pic only to prove it happened)


This is the TT adjustable bar from MOSS. I wish it weren't blue, but I suppose I can fix that later. I'm set up on the maximum stiffness. For me, the best way to find out what too stiff feels like is to max this bar, drive it and learn something. If it is really bad, I could reduce the stiffness really easily.

At full wheel droop, the ASB rubs just slightly on the bump stop on the driver's side. This might be avoidable if I could move the bar slightly forward overall. The bar does have adjustment in this direction possible. However, in order to move it forward at all I need to notch or remove the front tow brackets. You can see one of those brackets in the upper right of the pic above.

freetors Nick H
Collinsville, OK, USA   USA
1973 MG MGB
I really like the looks of those adjustable end links Brad. I wish I had some for the stock front bar. I can't stand those mushy, crude factory endlinks.

I don't tell this to many people because they don't understand it or think it's crazy, but I'm actually running a droop limited front suspension. I have steel cables that only let the front wheels droop about 2" IIRC. It's a poor man's swaybar. It sounds totally counter-intuitive but it does actually greatly reduce total body roll and at the same time reducing understeer, so in some ways it works to compliment the FSB, but it's effects are are different. Here's a description on some of the physics of it from username Purple Frog on apexspeed.com:

In reply to a post by Purple Frog ......So what happens in a non-droop limited car when you turn the wheel?

1 - A certain amount of weight is immeadiately transferred thru the suspension arms. G-loading starts, and roll begins.

2 - Roll continues until the forces balance each other. How far the car rolls is determined by CG height, roll center height, track width, roll resistance, and cornering force. How much weight is transferred is a function of the same.

If the car is softly sprung, the car will roll a lot. As a consequence, the roll center position changes according to the suspension geometry. At the front, it will generally get lower,( becase of the "dive" from brking) and will usually move sideways a bit (sometimes quite a bit). As the roll center goes lower, the built in roll resistance is decreased, and the car rolls farther, and so on. At the same time, the rear roll center will rise as the suspension rises from the braking forces. As it rises, it's roll resistance increases, but more importantly, the amount of weight transfer to the front also increases.

If the transfer is too much, the front outside tire has too much weight transferred onto it, and at the same time the front suspension is also being asked to contribute more than it's fair share to the overall roll resistance couple. The result is a sloppy feeling car with a lot of push.

In the droop limited car, Geometric weight transfer also takes place immeadiately, but then things change a bit.

Since the inside wheel is already at full droop, the car can no longer roll about the roll center. If the car is to roll at all, the pivot point becomes the contact patch of the inside tire. This actually will raise the amount of Geometric roll resistance a fair amount, and the car won't roll as far. But more important is what happens to the effecive rate of the sway bar - it is cut in HALF! How?

Remember that the inside wheel cannot go into droop so the lever arm on that side of the bar is now in a fixed position. The only twist introduced into the sway bar is now solely thru the outer lever arm, and so the bar's contribution to roll resistance is cut in half. The overall roll resistance couple is biased more to the rear now, and the car doesn't develop as much push.

Another phenomenon that happens is that more weight stays on the inside wheel, so it can now contribute more traction than it could before. Remember that the contact patch is now the roll pivot point - for the car to roll at all, a certain amount of weight has to be on that patch. If the tire is completely unloaded, the roll pivot point then becomes the outer contact patch. When that happens, the car will stop rolling, and raise the inside tire off of the ground, at which point you can't corner any faster.

If you add preload to the springs, you accomplish 2 things :

1- the nose won't dive as far under braking. Rear-to-front weight transfer still happens,but will be decreased slightly - the max pitch attitude is decreased (the nose doesn't dive as much) so the front roll center stays higher, because the weight transferred first has to overcome the amount of the preload.

2- Roll stops sooner as the inside tire has less droop available.

If the springs are preloaded enough, the amount of Geometric weight transfer is increased, which results in the faster reactions at the front

If the springs are preloaded too much (such as that the nose doesn't dive at all under braking), then the Geometric weight transfer phenomemon becomes the sole means of weight transfer , and quicky overloads the tire contact patches, resulting a "skatey" and "darty" car.

The "sweet spot" is where the car is still able to dive a bit under braking, leaving a bit of droop available for the inside tire. The car will still roll a bit, according to the amount of cornering force produced, but the inside tire will run out of droop travel at exactly the right g-loading where push would usually start ( remember the halving of the sway bar rate & the resultant roll couple balance) ......

Thurlowb Avatar
Thurlowb Silver Member Brad Thurlow
Coquitlam, British Columbia, Canada   CAN
That is a lot to absorb. Seems the more I read about suspension theory the less I know.

freetors Nick H
Collinsville, OK, USA   USA
1973 MG MGB
I will also add that I can't tell one bit of difference in ride quality with that mod either.

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