MC Kramppi Scientific Bike Research Center:

 MTB Tires; rolling resistance, snakebite resistance etc. - an analysis based on tire test on Bike 08/2004

The German Bike magazine tested 26 mountain bike tires on their August 2004 issue. As always the Germans were pretty thorough and they tested for example the rolling resistance and snakebite resistance of the tires. The research team of MC Kramppi Scientific Bike Research Center (MCKSBRC) was once again sent to their research facilities to make further analyses based on the testing data of the tire test. 

The analyses concentrate on finding answers to the following questions:

1        Which factors have the biggest impact on the rolling resistance of the tires? The weight, width or maybe some other factors? On which tires the ratio between the rolling resistance and the weight is the best? How about the ratio between the rolling resistance and the width of the tires?

2       Which factors contribute the most on the snakebite resistance of the tires? Which tires have the best snakebite resistance compared to the weight of the tire?

3        Does the actual grip of the tires correlate in any ways with the rolling resistance?

This analysis is a follow up on the analyses based on the tire test which appeared on the Bike magazine 09/2002. However that research is only available in Finnish language.

Our reserch team spent couple of weeks on their research facilities and now they have stepped back into the fresh air and they have published the results of their analyses. The report of their research consists of the following sections:

The background and the basic assumptions of the analyses

1. Rolling resistance

2. Snakebite resistance

3. Grip and rolling resistance

Conclusions and summary of the analyses

The backgroung and the basic assumptions of the analyses

The analyses are based on the information published on the German Bike magazine (issue 08/2004 pages 42-51). The test tires were divided into three categories: Cross Country (XC), Enduro/Allround (EN) and Freeride (FR). On the following analyses the freeride tires (6 tires) have been excluded and only the XC tires (8 tires) and the enduro tires (12 tires) were included in the analyses.

The tires and their weight:

The magazine performed tests on the rolling resistance (rollwiderstand) and snakebite resistance (durchschlagsschutz) of the tires.  The rolling resistance and the snakebite resistance of each tire was measured in laboratory conditions. Other test criteria included two different star ratings based on the grip of the tires; Kurvenhalt and Traktion. The tires received 1 to 6 stars on these criteria. A six step grading system was also used to give the overall verdict on the tires. 

The magazine also measured the actual weight and the width of the tires. These two measurements were used as explanatory variables in the analyses. On this year's test the magazine didn't measure the actual height of the tires like it did on their 2002 test.

MC Kramppi Scientific Bike Research Center wanted to find out more on the correlations between the rolling resistance, snakebite resistance and the factors behind low rolling resistance and high snakebite resistance. The research team also wanted to know which tires have managed to optimize these factors the best. 

1. Rolling resistance

The research team tried to find out how big impact the widht and the weight of the tire has on the rolling resistance of the tire.

K11 Rolling resistance

The correlation coefficient between the actual width (carcass) and the rolling resistance. was only 0,12. The correlation coefficient between the actual weight and the rolling resistance was 0,32. This means that based on these results there were no significant correlation between these factors. 

The research team also analysed which tires have done well in optimizing width and rolling resistance and weight and rolling resistance. The analysis was performed by calculating an index number on each tire and each factor. The index was based on the average value of each factor. This means that if for example a tire had 10 percent better (ie. lower) rolling resistance than an average tire it would have and index number of 110. If a tire was wider than an average tire it would have a higher index number. If a tire was heavier than an average tire it would also have a higher index number. 

Based on these index numbers a ratio between the width and rolling resistance and weight and rolling resistance was calculated. A similar index  based analysis has been used in other analyses too.

The index numbers based on the width and rolling resistance is as follows:

K12 Rolling resistance and width

Michelin Comp S Light (index 110), Hutchinson Spider Air Light (110) and Nokian NBX (110) had the best ratio between the width and the rolling resistance. This means that they had managed to optimize rolling resistance with the width of the tire. However the differences between these and other top tires were reasonably small. By far the worst tires were Kenda Nevegal (76) and Specialized Rockster Pro (81). 

When measuring the ratio between the rolling resistance and the weight of the tire following results were found:

K13 Rolling resistance and weight

Schwalbe Big Betty (116) and Hutchinson Spider Air Light (114) were the best tires when measuring the ratio between the rolling resistance and the weight of the tires. Schwalbe was also the heaviest tire of the test (889 g). The worse tires once again were Specialized Rockster Pro and Kenda Nevegal. The differences between the tires on this ratio were much bigger than on the rolling resistance and width ratio.

The ratios between the rolling resistance and the snakebite resistance:

K14 Rolling resistance and snakebite resistance

Schwalbe Big Betty (140), Ritchey Moto Vader Pro (125) and Continental Gravity Pro (122) had the best ratio between the rolling resistance and the snakebite resistance. The worst tires were once again Specialized Rockster Pro (73) and Kenda Nevegal (75).

2. Snakebite resistance

The research team also analyzed how big impact the width and the weight of the tires has on the snakebite resistance of the tires.

The tires and their snakebite resistance:

K21 Snakebite resistance

Both the width and the weight of the tires had significant correlation to the snakebite resistance of the tires. The correlation coefficient between the width and the snakebite resistance was 0,77 and between the weight and the snabebite resistance 0,73.

The ratio between the snakebite resistance and the width of each tire was calculated so that a narrow tire with a good snakebite resistance received a good index number. The same applies to a light tire with good snakebite resistance.

The ratios between the snakebite resistance and the width of the tire were:

K22 Snakebite resistance and width

Once again the best tire was Schwalbe Big Betty (139). The next best tires were Ritchey Moto Vader (125) and Continental Gravity Pro (114). The worse tires were Hutchinson Spider Air Light (87), Continental Explorer Supersonic (88) and Continental Leader Protection (88).

The ratios between the snakebite resistance and the weight of the tire were:

K23 Sb ja paino

The top two tires were Schwalbe Big Betty (124) and Ritchey Moto Vader (118) - the same tires as on the previous measurement. The worst tire was Hutchinson Spider Air Light (83) followed by IRC Trailbear (86) and Nokian NBX (88).

3. Grip and rolling resistance

On this analysis the research team summarized the two grip ratings which were given to the tires. This variable was analysed against the rolling resistance of the tires. The correlation coefficient between these two variables was 0,28 which means that there was no significant correlation between the grip and the rolling resistance.

A index number for each individual tire was also calculated:

K31 Rolling resistance and grip

Four tires which had the best ratio between the grip and the rolling resistance were Michelin Comp S Light (118), Schwalbe Fat Albert (114), Continental Explorer Supersonic (109) and Continental Gravity Pro (109). There were three tires which had significantly low value on this analysis: Specialized Rockster Pro (70), Kenda Nevegal (86) and Hutchinson Spider Air Light (89).

Conclusions and summary of the analyses

Rolling resistance

There were no significant correlation between the width and the rolling resistance of the tires or between the weight and the rolling resistance.

Of the 20 analysed tires Michelin Comp S Light, Hutchinson Spider Air Light and Nokian NBX had the best ratio between the width and the rolling resistance.  Schwalbe Big Betty and Hutchinson Spider Air Light were the best tires when measuring the ratio between the rolling resistance and the weight of the tires. Schwalbe Big Betty, Ritchey Moto Vader Pro and Continental Gravity Pro had the best ratio between the rolling resistance and the snakebite resistance.On all three analyses the worst tires were Kenda Nevegal and Specialized Rockster Pro.

Snakebite resistance

Both the width and the weight of the tires had significant correlation to the snakebite resistance of the tires. 

On the ratio between the snakebite resistance and the width and also on the ratio between the snakebite resitance and the weight of the tires the best tires were Schwalbe Big Betty and Ritchey Moto Vader. The worse tires were Hutchinson Spider Air Light and Continental Explorer Supersonic (snakebite vs. width) and Hutchinson Spider Air Light and IRC Trailbear (snakebite vs. weight)

Grip and rolling resistance

The research team found no significant correlation between the grip and the rolling resistance of the tires. 

The four tires with the best ratio between the grip and the rolling resistance were Michelin Comp S Light, Schwalbe Fat Albert, Continental Explorer Supersonic and Continental Gravity Pro. There were three tires which had significantly low value on this analysis: Specialized Rockster Pro, Kenda Nevegal and Hutchinson Spider Air Light.

 

Text: Portti