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INTRODUCING the RENNtorq Center Lock Removal Tool for 991/997 applications
After purchased my dream car last fall, a 991.1 GT3, I quickly fell in love with every aspect of it except one thing - wheel removal. Using the conventional long breaker bar/torque wrench combo, along with the need to have the car running and a 2nd person inside to assist, left something to be desired. I needed to find a better way.
As a number of youtube videos show, the Porsche factory uses a more elegant, quicker and safer method to mount the wheels on the GT3 assembly line. Their system uses a electrically driven torque multiplier along with a custom reaction arm to apply torque to the nut.
A similar concept was used to develop the new tool shown in the video below called the RENNtorq Center Lock Removal Tool. The tool greatly simplifies the wheel removal and installation process for 991.1/.2 GT3/GT3RS/GT2RS models, and fits 997.2 GT3/GT3RS models as well. A motorsport grade torque multiplier is used the convert 95 lb-ft of manual input torque to 443 lb-ft of output torque. The torque multiplier has a 1/2" drive input, and a 3/4" drive output which allows for a direct connection to the factory supplied socket. Each multiplier is tested and certified to a specific multiplication factor (roughly 4.7:1) which allows you to precisely calculate the input torque required to secure the center lock nut. A custom reaction arm counteracts the torque applied to the nut by applying a counter force to the spoke of the wheel. The reaction arm is covered with a polymer material strong enough to apply the required force, but soft enough to eliminate any risk of wheel damage. The system allows you to easily remove the center lock nut with just a conventional 20" long, 1/2" drive breaker bar/torque wrench with an amount of force similar to what is required to remove a lug on a car with a regular five lug bolt system. The RENNtorq tool requires only moderate pressure be applied to the brake pedal inside the car, meaning the car does NOT need to be running, and you do not require the assistance of a second person to either press the brake hard or hold the steering wheel steady.
The prototype for the tool has been beta tested at a Porsche dealership for about a month and a half and they have decided to purchase it. The service manager liked that the tool turned wheel removal into a straight forward one man job, and that he didn't need to pull anyone off other work to assist with wheel removal or installation. I will be manufacturing more units for myself and for a few others, and there will be a few additional units available if anyone else on Rennlist would like one. The price of the unit is driven by the motorsport grade torque multiplier (light weight, certified, capable of 700 lb-ft+ if needed to break lose stuck nuts) and the custom nature of the reaction arm. For those interested in getting one of these tools during my next manufacturing run the price will be $2,200 which will include a case, certification, and the tool. No more dreading the removal of your center locks - it's now as simple as working on a 5-lug Porsche.
will this work on 991.1 GTS wheels? I ask because I am not sure if that white piece will fit between the spokes.....any way you can confirm for us?
Yes it will. I have made up separate reaction arm cylinders (the white part) for GTS and Turbo S wheels that have smaller spoke openings than GT3s. If you have one of those two cars just let me know and I'll make sure you get the correct version.
I've looked at torque multipliers, but found that their confidence interval was too wide to be acceptable to me. Typically, a torque wrench is accurate to +/- 4-6%. I've found that all the torque multipliers can lose an additional 10-20% due to friction. What are the confidence intervals in this RENNtorque torque multiplier? How much is lost to friction in this device? Thanks.
I've looked at torque multipliers, but found that their confidence interval was too wide to be acceptable to me. Typically, a torque wrench is accurate to +/- 4-6%. I've found that all the torque multipliers can lose an additional 10-20% due to friction. What are the confidence intervals in this RENNtorque torque multiplier? How much is lost to friction in this device? Thanks.
There are a lot of torque multipliers out there - some are tightly spec'ed and some are not.
Selection of the right torque multiplier was a key element in developing this tool. After a lot of investigation we went with a very highly spec'ed unit, which is individually certified on a test rig. The multiplier we went with is also the smallest/lightest unit available world-wide that meets our 700 lb-ft torque requirement, with the required input and output drive sizes.
Below is an actual multiplier certification which shows it's calibration curve at three different torque levels (in N-m), and shows a mean multiplication factor of 4.73:1. The multiplier manufacturer certifies the unit to +/- 4% (which is the same quoted by the manufacturer of the typical 'long torque wrench' solution), but you can see from the actual data that it is a lot tighter than that. The measured variation in the torque range we will be using is less than +/-2%. This is a motorsport grade multiplier, with the best known performance currently available in the market.
If you have other questions on this just let me know.
There are a lot of torque multipliers out there - some are tightly spec'ed and some are not.
Selection of the right torque multiplier was a key element in developing this tool. After a lot of investigation we went with a very highly spec'ed unit, which is individually certified on a test rig. The multiplier we went with is also the smallest/lightest unit available world-wide that meets our 700 lb-ft torque requirement, with the required input and output drive sizes.
Below is an actual multiplier certification which shows it's calibration curve at three different torque levels (in N-m), and shows a mean multiplication factor of 4.73:1. The multiplier manufacturer certifies the unit to +/- 4% (which is the same quoted by the manufacturer of the typical 'long torque wrench' solution), but you can see from the actual data that it is a lot tighter than that. The measured variation in the torque range we will be using is less than +/-2%. This is a motorsport grade multiplier, with the best known performance currently available in the market.
If you have other questions on this just let me know.
Looks like a great tool! I'm still not certain about the accuracy, though, as at the very least, it is less accurate than the torque wrench that is used in conjuction with it, which is +/-4-6%, with possibly an additional +/-2-4% lost in the multiplier. I'm not an expert, but I would surmise that it would probably be fine for motorsport uses. At $2200, the price is probably prohibitive for anyone except dealerships; I would imagine that you could sell quite a few of those if you could find a way to bring the price down closer to $500. Best wishes!
Looks like a great tool! I'm still not certain about the accuracy, though, as at the very least, it is less accurate than the torque wrench that is used in conjuction with it, which is +/-4-6%, with possibly an additional +/-2-4% lost in the multiplier. I'm not an expert, but I would surmise that it would probably be fine for motorsport uses. At $2200, the price is probably prohibitive for anyone except dealerships; I would imagine that you could sell quite a few of those if you could find a way to bring the price down closer to $500. Best wishes!
Thanks for your comments. On a board where there are plenty of $10k exhausts and wheel sets being purchased, there are likely a number of folks that would not be bothered by the price point if they see value in what the tool brings to them. In my case it was the first aftermarket money I spent on the car ahead of things like wheels, exhaust, etc. that I intended on purchasing. Initial interest has been strong but ultimately the market will decide!
Thanks for your comments. On a board where there are plenty of $10k exhausts and wheel sets being purchased, there are likely a number of folks that would not be bothered with the price point if they see value in what the tool brings to them. In my case it was the first aftermarket money I spent on the car ahead of things like wheels, exhaust, etc. that I intended on purchasing. Initial interest has been strong but ultimately the market will decide!
I did a 5-lug conversion on my 997. Many, many other folks have done it too. That cost me much more than $2500, for materials, labor and wheels.
I have used a torque multiplier since my 997.2 GT3 with no issues regarding accuracy. If you take into account the stacked error- ie overtighten by that small amount you are at worst over by the error or best case right on the money. Those above worried about an extra 2% error please show me the calibration cert. for your torque wrench that’s no more than 6 months old (NIST traceable of course) AND show me how you use your torque wrench - most abuse them terribly.
OK- enough ranting. My question for the OP is the force on the lever arm. I have had enough force loosening a wheel to divot concrete with my lever arm- are we in a safe range for the wheel spokes?
06-12-2019, 10:19 PM
INTRODUCING the RENNtorq Center Lock Removal Tool for 991/997 applications
