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Discussion Starter #1
Hey guys,

I have tried searching here and Google and Youtube but I get results relating mainly to quarter mile drag racing. I'm probably getting the keywords incorrect, so apologies if this is a duplicate post, but please point me in the right direction, if so.

On to my question:

I will be entering my bike on a 800m (half mile) top speed competition on September 8th. It's my first time riding my bike in competition. The winner is the one with the highest top speed. So although you may be racing a competitor, you could still win the race (and event) by getting a higher speed, as opposed to a quicker ET or winning heads up.

Firstly, what is the relationship between acceleration and top speed? I have been told that "launching" as if you're racing a quarter mile actually reduces top speed. Why is this? And what would be the best way to accelerate down the strip for this type of racing?

Secondly, what tips do you have for me to get the best top speed possible. My bike is completely stock apart from 520 lightweight chain and sprockets, DNA air filter, and Akra slip on. I have standard (close to replacement) Bridgestone S20 evos on the standard cast rims. My bike recently dyno'd at 197hp/117Nm on a local dyno (I'm in Cape Town South Africa) - yes I know it's just a number. No flash. No piggy back fuelling.

Would it help me to remove as much weight as possible like the indicators and mirrors and passenger footpegs and number plate cluster etc? Would it help if I had the bike lowered (just for the day as I still enjoy the all round ability of my bike). Should I over inflate or deflate the tyres? What should the DDC suspension settings be?

I have a bubble dark tint screen that I can't see through so I'm thinking of putting the stock clear screen back on, but I'm not exactly tiny. A friend suggested I use the bigger screen but "peek through the side" because I'm not on the street, but I don't know about that. I like my skin unblemished and on my body. I understand the importance of a good tuck but what would be a good compromise here (short of testing out both setups on the day)?

So any tips or advice would be great.

I'm doing this for fun and have no delusions of being the fastest guy there. It's my very first time doing anything like this, but I just wanna be sure that I have all the basics right to do the best I can.

Thanks in advance guys.
 

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Best things i have found out to help trap speed are keep your tuck game strong. Chin against the tank, elbows in, knees in. Make sure you wind first gear all the way out. Dont short shift.
 

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Do full drag race launch. Don't short shift. Practice this. It's difficult to get the optimal clutch release, control the wheelie (especially for a non-lowered/extended bike), etc. Though don't burn out your clutch. With that said, a good launch will benefit the ET way more than top speed, but it still helps speed a bit.

For top speed, yes get rid of mirrors, etc. but mostly to reduce their aero drag than weight. Go clear screen for full tuck. Wear a sport helmet where you can see (up) in full tuck. You can help this by inserting some foam into the top of your helmet that pushes the helmet higher onto your head and gives more clearance at the eyebrow level.
 

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Discussion Starter #5
Just an update on this for those of you interested.

So I did this yesterday 8 September and results were great.

I removed mirrors, indicators, tail tidy cluster, tools, and fitted standard clear screen. Had minimal fuel in the bike (not sure how accurate I was but bike was certainly lighter. Put some foam in the top of the helmet as suggested and tried the tips you guys listed here.

Tucked as best I could and deactivated tc after 2nd run once I had overcome my fear of flipping the bike. Nice easy controlled take offs (no hard launching) and first got comfortable with wot and then my tuck got better and then also I was able to get to full throttle earlier as the day progressed. 8 runs in total.

Although i was by far the slowest, compared to all the modded bikes who were all at least flashed and lowered, I did a best pass of 281.3kph.

I am over the moon with my bikes performance and I'm going to try a lot of other things first before I even begin to fiddle with the ECU or engine. Strap the front, lose some body fat, get better gloves etc. Such a lot of fun things to try to improve.

I found I really liked this format of racing and hopefully I can advance enough to maximise the bike before searching for max power.

Top NA 1000cc for the day was 295kph (built K7 suzuki), 2nd and 3rd a couple bmws in 290's 2012 and 2015 models respectively. And then a 288 from a 2015 beemer and 285 from a 2017. I was the only "stockish" bike bar my exhaust, dna air filter and 520 chain and 17/45 sprockets. No idea where the other manufacturers were. 🤷‍♂️

Great fun. Any tips for improvement or criticism welcomed.
 

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Congrats on having the courage to attempt it! Good for you on your speed and it's nice to hear you enjoyed it! Nice to hear some other BMW's were posting high speeds.

Did anyone happen to get photos/video of you while doing this that you could post? Maybe if you had video some people could better give advice on form or launching to aid you.
 

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Discussion Starter #7
Congrats on having the courage to attempt it! Good for you on your speed and it's nice to hear you enjoyed it! Nice to hear some other BMW's were posting high speeds.

Did anyone happen to get photos/video of you while doing this that you could post? Maybe if you had video some people could better give advice on form or launching to aid you.
Hey savage. I don't really have any videos. Here and there I was sent a whatsapp vid from spectators but whatsapp reduces the quality so much that it's hard to see any great detail and the focus wasn't necessarily directly on me. If I get some fair quality vids I'll be sure to post.
 

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Discussion Starter #8
Hey again guys,

So a google search and a search of this forum gets me pretty much nowhere because it doesn’t seem like this form of racing is very popular. I don't quite get the info I'm looking for. So I’m putting this here.

So we have another 800m top speed event on the same air field at the end of November. I’m entering again to try and better my best speed of 281kph. I won’t be fettling with the ECU just yet, but I will be trying a few new things to go faster.

I’ll again remove the indicators etc. as per the last event but I’ve identified some additional weight savings I could make (every bit helps right?). I won’t be lowering on the links and/or forks but will be using a strap next time.

But my question relates specifically to tyre size changes and sprocket changes.

I’d like to know the following:

Tires: I have the choice of getting some ex race tires. The first is a set of supercorsas with a rear tire in 200/55/17 size. The second is a set of metzeler racetecs with a 180/60/17 rear.

On both occasions the front is a 120/70/17 matching brand.

If nothing changes other than tire size, then which one should theoretically give me the higher speed at 800m/half-mile? Standard size currently is a 120/70/17 front with a 190/55/17 rear (s20 evo). I’ve been told the 180/60/17 is almost identical in size to the 190/55/17.

Second question relates to sprocket changes. I won’t be changing the front sprocket. I just want to go up one or down one tooth in the rear. I know that going down 1 tooth to 44 will give me marginally higher top speed at the expense of a bit of acceleration and doing the opposite (i.e. one tooth up to 46) will give me marginal acceleration at the expense of a bit of top speed.

I have tried the various permutations on Gearing Commander and although I can see how the top speeds are affected by the changes, it accounts for your specific speed at peak power (13 500rpm). I am not really smart enough to calculate what this means for me at 800m.

FWIW, when riding through the gears with stock sprockets and 195/55/17 tyre, I get to 6th gear around 200m or so before the 800m line. At least it appears to be that sort of distance. One makes up quite a bit of ground at those speeds.

Said another way, I hit sixth and then it’s a few moments before I cross the line with plenty of revs left in 6th.

So to me it would seem that I can sacrifice a little bit of ultimate top speed because I doubt I’ll get to 300kph + over 800m without adding more power or revs. So going one tooth up in the rear seems to be the better option because I should get through a few more revs in 6th without hitting limiter before the line. Is this a correct assumption. Remember, I have virtually no clue on these things yet. And neither would my competitors it seems wink wink
 
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